'Strong, concrete suspicions': UN investigator Carla del Ponte says there are indications that chemical weapons attacks were carried out by Syrian rebels . A senior United Nations official has claimed that Syrian rebels may have used chemical weapons against government forces. Carla Del Ponte said evidence from casualties and medical staff indicated that rebel forces in the civil war had used the deadly nerve agent sarin. ‘Our investigators have been in neighbouring countries interviewing victims, doctors and field hospitals, and there are strong, concrete suspicions, but not yet incontrovertible proof, of the use of sarin gas,’ said Del Ponte in an interview with Swiss-Italian television. ‘This was use on the part of the opposition, the rebels, not by the government authorities.’ Last night, the UN commission looking into allegations of war crimes in Syria tried to row back on the comments by its human rights investigator, pointing out that conclusive evidence had not been discovered. However, the White House said it was likely that President Bashar al-Assad’s regime, not the rebels, were behind any chemical weapons use. Syrian government forces and the rebels have already accused each other of carrying out three attacks with chemical weapons. Sarin has been classed as a weapon of mass destruction due to its potency and is banned under international law. US President Barack Obama has said that the use or deployment of chemical weapons in Syria would cross a ‘red line’ that could lead to foreign military intervention. Following two Israeli air strikes on military bases in the Syrian capital Damascus over the weekend, a Russian foreign ministry spokesman said: ‘We are seriously concerned by the signs of preparation for possible armed intervention in Syria.’ As a long-standing Syrian ally, Russia has protected President Assad by blocking Western efforts in the UN Security Council to push him from power. Israeli officials claim the air strikes were to ensure Lebanon’s Hezbollah did not receive a shipment of hi-tech missiles that could threaten Israel. The comments by Ms Del Ponte, a member of the U.N. panel probing alleged war crimes in Syria, contradict claims by Britain and the U.S. that intelligence reports showed Syrian soldiers had used chemical weapons. She said that the United Nations independent commission of inquiry on Syria has not yet seen evidence of government forces having used chemical weapons, which are banned under international law. 'Our investigators have been in neighbouring countries interviewing victims, doctors and field hospitals and, according to their report of last week which I have seen, there are strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas, from the way the victims were treated,' said Ms Del Ponte. The odourless, colourless nerve agent prevents the proper operation of the enzyme acetylcholinesterase, the nervous system's 'off switch' for glands and muscles. Without this enzyme muscles are continually stimulated leading to convulsions, paralysis, unconsciousness and eventually respiratory failure leading to death. Ms Del Ponte, a former Swiss attorney-general who also served as prosecutor of the International Criminal Tribunal for the former Yugoslavia, gave no details as to when or where sarin may have been used. Assad's government and the rebels accuse each another of carrying out three chemical weapon attacks, one near Aleppo and another near Damascus, both in March, and another in Homs in December. Horrific: Experts have said that the injuries shown in the video, which emerged last month, are consistent with those sustained after a chemical weapon attack . Graphic: The video was posted on the Facebook page of British-trained doctor Niazi Habash, who treated some of the victims of the strike, which was said to have hit the northern city of Aleppo . Victim: A woman is treated for what appears to be breathing difficulties at a clinic in the north of Aleppo. Rebels blamed government forces for the attack, but a UN Commission suspects they carried it out themselves . Meanwhile fighting continued to rage in Syria, where rebels claimed to have killed eight government troops after shooting down their helicopter in the eastern province of Deir el-Zour, along Syria's border with Iraq. The Coventry-based Syrian Observatory for Human Rights posted footage online showing several armed men standing in front of the wreckage. As one of the fighters in the video speaks, the camera pans to a pick-up truck piled with bodies. The fighter is then heard saying that all of Assad's troops who were on board the helicopter were killed as it crashed. He says Islamic fighters of the Abu Bakr Saddiq brigade brought down the helicopter as it was taking off from a nearby air base in the provincial capital. The Observatory, which claims to get its information via a network of activists on the ground, said eight troops were killed in the incident yesterday. Downed: In this image taken from a video obtained from the Shaam News Network, armed men stand near the wreckage of a military helicopter, left, in Deir el-Zour, which was said to have contained eight regime soldiers . Narrative: The soldier speaking in the video says Islamic fighters of the Abu Bakr Saddiq brigade brought down the helicopter as it was taking off from a nearby air base in the provincial capital . Rebels also yesterday occupied parts of the Mannagh military air base after weeks of fighting with government troops who have for months been defending the sprawling facility near the border with Turkey. Assad's warplanes were pounding rebel positions inside the base on today as battles between rebels and government forces raged on, the Observatory said, adding there was an unknown number of casualties on both sides. The rebels moved deep into the air base yesterday despite fire from government warplanes, capturing a tank unit inside and killing the base commander, claimed the Aleppo Media Centre, another activist group. The fighting comes a day after Israeli warplanes struck areas in and around the capital, Damascus, setting off a series of explosions as they targeted a shipment of guided missiles believed to be bound for Hezbollah. The airstrike, the second in three days and the third this year, signalled a sharp escalation of Israel's involvement in Syria's civil war. Aftermath: Bulldozers work to remove rubble after the Israeli airstrike in the Al-Hama area near Damascus which Israeli military authorities said targeted a shipment of guided missiles believed to be bound for Hezbollah . Destruction: The damage left at a chicken farm building following the attack. The airstrike, the second in three days and the third this year, signalled a sharp escalation of Israel's involvement in Syria's civil war . Syrian state media reported that Israeli missiles hit a military and scientific research centre near Damascus and caused casualties. The reports did not specify the number or say if the casualties were civilians or troops. The state-run Sana news agency made no mention of the fighting inside the Mannagh air base. But it reported that government troops today regained control of villages along the highway linking the northern city of Aleppo to its civilian airport, the country's second largest. Syrian 'armed forces restored security and stability to (six) villages' south of the city and along the airport highway, Sana said, calling it a 'major strategic victory in the north'. Much of the north has been in opposition hands since rebels launched an offensive in the area last summer, seizing army bases, large swathes of land along the border with Turkey and whole neighbourhoods inside Aleppo. The Syrian conflict started in 2011 with protests against Assad's regime, but eventually turned into a civil war that according to UN estimates has so far killed more than 70,000 people. More than one million Syrians have fled their homes during the fighting and sought shelter in neighbouring countries such as Jordan, Lebanon and Turkey. Millions of others have been displaced inside the country.
Carla Del Ponte said UN Commission investigating war crimes in Syria has 'strong, concrete suspicions' that rebels used chemical weapons .
Her remarks contradict statements by the U.S. and UK which said intelligence indicated Syrian soldiers used the weapons .
Today fighting continued across Syria as rebels advanced on a northern airbase and shot down helicopter in the east .
'Strong, concrete suspicions': UN investigator Carla del Ponte says there are indications that chemical weapons attacks were carried out by Syrian rebels . A senior United Nations official has claimed that Syrian rebels may have used chemical weapons against government forces. Carla Del Ponte said evidence from casualties and medical staff indicated that rebel forces in the civil war had used the deadly nerve agent sarin. ‘Our investigators have been in neighbouring countries interviewing victims, doctors and field hospitals, and there are strong, concrete suspicions, but not yet incontrovertible proof, of the use of sarin gas,’ said Del Ponte in an interview with Swiss-Italian television. ‘This was use on the part of the opposition, the rebels, not by the government authorities.’ Last night, the UN commission looking into allegations of war crimes in Syria tried to row back on the comments by its human rights investigator, pointing out that conclusive evidence had not been discovered. However, the White House said it was likely that President Bashar al-Assad’s regime, not the rebels, were behind any chemical weapons use. Syrian government forces and the rebels have already accused each other of carrying out three attacks with chemical weapons. Sarin has been classed as a weapon of mass destruction due to its potency and is banned under international law. US President Barack Obama has said that the use or deployment of chemical weapons in Syria would cross a ‘red line’ that could lead to foreign military intervention. Following two Israeli air strikes on military bases in the Syrian capital Damascus over the weekend, a Russian foreign ministry spokesman said: ‘We are seriously concerned by the signs of preparation for possible armed intervention in Syria.’ As a long-standing Syrian ally, Russia has protected President Assad by blocking Western efforts in the UN Security Council to push him from power. Israeli officials claim the air strikes were to ensure Lebanon’s Hezbollah did not receive a shipment of hi-tech missiles that could threaten Israel. The comments by Ms Del Ponte, a member of the U.N. panel probing alleged war crimes in Syria, contradict claims by Britain and the U.S. that intelligence reports showed Syrian soldiers had used chemical weapons. She said that the United Nations independent commission of inquiry on Syria has not yet seen evidence of government forces having used chemical weapons, which are banned under international law. 'Our investigators have been in neighbouring countries interviewing victims, doctors and field hospitals and, according to their report of last week which I have seen, there are strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas, from the way the victims were treated,' said Ms Del Ponte. The odourless, colourless nerve agent prevents the proper operation of the enzyme acetylcholinesterase, the nervous system's 'off switch' for glands and muscles. Without this enzyme muscles are continually stimulated leading to convulsions, paralysis, unconsciousness and eventually respiratory failure leading to death. Ms Del Ponte, a former Swiss attorney-general who also served as prosecutor of the International Criminal Tribunal for the former Yugoslavia, gave no details as to when or where sarin may have been used. Assad's government and the rebels accuse each another of carrying out three chemical weapon attacks, one near Aleppo and another near Damascus, both in March, and another in Homs in December. Horrific: Experts have said that the injuries shown in the video, which emerged last month, are consistent with those sustained after a chemical weapon attack . Graphic: The video was posted on the Facebook page of British-trained doctor Niazi Habash, who treated some of the victims of the strike, which was said to have hit the northern city of Aleppo . Victim: A woman is treated for what appears to be breathing difficulties at a clinic in the north of Aleppo. Rebels blamed government forces for the attack, but a UN Commission suspects they carried it out themselves . Meanwhile fighting continued to rage in Syria, where rebels claimed to have killed eight government troops after shooting down their helicopter in the eastern province of Deir el-Zour, along Syria's border with Iraq. The Coventry-based Syrian Observatory for Human Rights posted footage online showing several armed men standing in front of the wreckage. As one of the fighters in the video speaks, the camera pans to a pick-up truck piled with bodies. The fighter is then heard saying that all of Assad's troops who were on board the helicopter were killed as it crashed. He says Islamic fighters of the Abu Bakr Saddiq brigade brought down the helicopter as it was taking off from a nearby air base in the provincial capital. The Observatory, which claims to get its information via a network of activists on the ground, said eight troops were killed in the incident yesterday. Downed: In this image taken from a video obtained from the Shaam News Network, armed men stand near the wreckage of a military helicopter, left, in Deir el-Zour, which was said to have contained eight regime soldiers . Narrative: The soldier speaking in the video says Islamic fighters of the Abu Bakr Saddiq brigade brought down the helicopter as it was taking off from a nearby air base in the provincial capital . Rebels also yesterday occupied parts of the Mannagh military air base after weeks of fighting with government troops who have for months been defending the sprawling facility near the border with Turkey. Assad's warplanes were pounding rebel positions inside the base on today as battles between rebels and government forces raged on, the Observatory said, adding there was an unknown number of casualties on both sides. The rebels moved deep into the air base yesterday despite fire from government warplanes, capturing a tank unit inside and killing the base commander, claimed the Aleppo Media Centre, another activist group. The fighting comes a day after Israeli warplanes struck areas in and around the capital, Damascus, setting off a series of explosions as they targeted a shipment of guided missiles believed to be bound for Hezbollah. The airstrike, the second in three days and the third this year, signalled a sharp escalation of Israel's involvement in Syria's civil war. Aftermath: Bulldozers work to remove rubble after the Israeli airstrike in the Al-Hama area near Damascus which Israeli military authorities said targeted a shipment of guided missiles believed to be bound for Hezbollah . Destruction: The damage left at a chicken farm building following the attack. The airstrike, the second in three days and the third this year, signalled a sharp escalation of Israel's involvement in Syria's civil war . Syrian state media reported that Israeli missiles hit a military and scientific research centre near Damascus and caused casualties. The reports did not specify the number or say if the casualties were civilians or troops. The state-run Sana news agency made no mention of the fighting inside the Mannagh air base. But it reported that government troops today regained control of villages along the highway linking the northern city of Aleppo to its civilian airport, the country's second largest. Syrian 'armed forces restored security and stability to (six) villages' south of the city and along the airport highway, Sana said, calling it a 'major strategic victory in the north'. Much of the north has been in opposition hands since rebels launched an offensive in the area last summer, seizing army bases, large swathes of land along the border with Turkey and whole neighbourhoods inside Aleppo. The Syrian conflict started in 2011 with protests against Assad's regime, but eventually turned into a civil war that according to UN estimates has so far killed more than 70,000 people. More than one million Syrians have fled their homes during the fighting and sought shelter in neighbouring countries such as Jordan, Lebanon and Turkey. Millions of others have been displaced inside the country.
Del Ponte said evidence from casualties and probing alleged war crimes in Syria, contradict claims by Britain and the U.S. that intelligence reports showed Syrian soldiers had used chemical independent commission of inquiry on Syria has used chemical weapons, which are banned under there are strong, concrete suspicions but not yet for the attack, but a UN Commission suspects they shooting down their helicopter in the eastern