Sweden's military is investigating reports of 'foreign underwater activity' in the Stockholm archipelago using high-tech-equipped naval vessels, aircraft and home guard forces. Chief of operations Jonas Wikstrom says information 'from a credible source' sparked the operation on Friday and was being investigated as part of a wider intelligence operation. Wikstrom refused to give further details about the operation, except saying the purpose was to find out whether 'there had been or still is ongoing foreign underwater activity'. Scroll down for video . Submarine hunt: Swedish forces search the murky waters of the Stockholm archipelago for the suspected foreign vessel off the Stockholm coast . He also declined to say whether they had been in contact with other countries. In a statement on The Local website, Wikstrom was quoted as saying: 'We have support for the analysis work we are now carrying out in the area in the form of ships, planes and territorial army personnel. 'The area is heavily trafficked, which is why it's important for us to go public with information about what we're doing.' The Local also quoted a witness to the military operation, Robert Eriksson, who was fishing off the island of Skarpö at around 4pm local time. Ready for action: A soldier mans a machine gun on a Swedish Navy fast-attack craft . 'The coast guard came in over the inlet with an airplane and flew round and round for a long time,' he said, adding that he also spotted a large military craft near the island of Kanholmsfjärden. Neutral Sweden's armed forces have ruled out that it could be some sort of natural phenomenon. The operation was reminiscent of the Cold War, when Sweden's armed forces routinely hunted for Soviet submarines in its waters. Locals using the waters for sailing and fishing reported an increase in military activity on Friday . The underwater activity comes in the wake of last month's aerial interception of Russian planes by UK jets. Royal Air Force jets were deployed from Scotland to intercept Russian military 'Bear' aircraft that were flying too close to the airspace it guards. Aircraft based at RAF Lossiemouth, based in Moray, were sent to identify the aircraft - Tu-95 Russian Bear H bombers - that were spotted in international airspace. A British Typhoon jet, bottom, is seen intercepting one of two Russian 'Bear' aircraft that were spotted flying in international airspace in September . On alert: Fast-attack craft cuts through the water as day breaks in Sweden's Stockholm archipelago . Chief of operations Jonas Wikstrom speaks at a press conference after reports of foreign underwater activity in the Stockholm Archipelago . It was the first time a Quick Reaction Alert had occurred since the base took on the role of defending the UK's Northern airspace. In June two Typhoon jets were scrambled into action to head off four separate groups of Russian aircraft that were flying near the Baltic. The jets were deployed to ensure the Russian planes didn't enter the airspace of Estonia, Lithuania or Latvia. The Ministry of Defence said the aircraft appeared to be carrying out a 'routine training' exercise in international airspace and were later escorted out of the area. That incident followed another where four Typhoons were sent to the Siauliai air base in Lithuania in May to support a Polish-led Nato force which was operating in the region. Sweden's military is investigating reports of foreign activity in the Stockholm archipelago, above, where Sweden's armed forces routinely hunted for Soviet submarines during the Cold War .
Sweden's military investigating reports of 'foreign underwater activity'
Chief of operations Jonas Wikstrom says information 'from credible source'
Search follows last month's interception of Russian airplanes by UK jets .
Sweden's military is investigating reports of 'foreign underwater activity' in the Stockholm archipelago using high-tech-equipped naval vessels, aircraft and home guard forces. Chief of operations Jonas Wikstrom says information 'from a credible source' sparked the operation on Friday and was being investigated as part of a wider intelligence operation. Wikstrom refused to give further details about the operation, except saying the purpose was to find out whether 'there had been or still is ongoing foreign underwater activity'. Scroll down for video . Submarine hunt: Swedish forces search the murky waters of the Stockholm archipelago for the suspected foreign vessel off the Stockholm coast . He also declined to say whether they had been in contact with other countries. In a statement on The Local website, Wikstrom was quoted as saying: 'We have support for the analysis work we are now carrying out in the area in the form of ships, planes and territorial army personnel. 'The area is heavily trafficked, which is why it's important for us to go public with information about what we're doing.' The Local also quoted a witness to the military operation, Robert Eriksson, who was fishing off the island of Skarpö at around 4pm local time. Ready for action: A soldier mans a machine gun on a Swedish Navy fast-attack craft . 'The coast guard came in over the inlet with an airplane and flew round and round for a long time,' he said, adding that he also spotted a large military craft near the island of Kanholmsfjärden. Neutral Sweden's armed forces have ruled out that it could be some sort of natural phenomenon. The operation was reminiscent of the Cold War, when Sweden's armed forces routinely hunted for Soviet submarines in its waters. Locals using the waters for sailing and fishing reported an increase in military activity on Friday . The underwater activity comes in the wake of last month's aerial interception of Russian planes by UK jets. Royal Air Force jets were deployed from Scotland to intercept Russian military 'Bear' aircraft that were flying too close to the airspace it guards. Aircraft based at RAF Lossiemouth, based in Moray, were sent to identify the aircraft - Tu-95 Russian Bear H bombers - that were spotted in international airspace. A British Typhoon jet, bottom, is seen intercepting one of two Russian 'Bear' aircraft that were spotted flying in international airspace in September . On alert: Fast-attack craft cuts through the water as day breaks in Sweden's Stockholm archipelago . Chief of operations Jonas Wikstrom speaks at a press conference after reports of foreign underwater activity in the Stockholm Archipelago . It was the first time a Quick Reaction Alert had occurred since the base took on the role of defending the UK's Northern airspace. In June two Typhoon jets were scrambled into action to head off four separate groups of Russian aircraft that were flying near the Baltic. The jets were deployed to ensure the Russian planes didn't enter the airspace of Estonia, Lithuania or Latvia. The Ministry of Defence said the aircraft appeared to be carrying out a 'routine training' exercise in international airspace and were later escorted out of the area. That incident followed another where four Typhoons were sent to the Siauliai air base in Lithuania in May to support a Polish-led Nato force which was operating in the region. Sweden's military is investigating reports of foreign activity in the Stockholm archipelago, above, where Sweden's armed forces routinely hunted for Soviet submarines during the Cold War .
Sweden's military is investigating reports of 'foreign underwater activity' in the Stockholm operations Jonas Wikstrom says information 'from wake of last month's aerial interception of Russian planes by UK jets. Royal Air Force jets reports of foreign activity in the Stockholm