United Arab Emirates forces have occupied sea and airports on Yemen's remote island of Socotra, a day after deploying four military craft and more than 100 troops there, according to a Yemeni government official.

Condemning the move as an "act of aggression", the official said UAE soldiers also blocked Ahmed Obeid bin Daghr, Yemen's prime minister, and 10 ministers from leaving Socotra on Friday.

"The UAE has occupied the airport and seaport of Socotra island, despite the Yemeni government's presence there. What the UAE is doing in Socotra is an act of aggression," the official told Al Jazeera.

Saudi Arabia has pledged to send investigators to Socotra, according to the official.

Socotra, a UNESCO heritage site home to some 60,000 people, has a 3,000-metre-long runway, ideal for fighter jets and large military aircraft.

The UAE recently leased the island for 99 years and has confirmed carrying out military operations there.

Residents of the island said the flag of the UAE and images of Crown Prince Mohammed bin Zayed Al Nahyan now adorn official buildings.

The deployment of Emirati troops on Thursday coincided with a rare visit to the strategically important island by Daghr.

Hundreds of islanders gathered to welcome Dagr on Thursday.

They denounced UAE presence on the island and chanted slogans in support of President Abd-Rabbu Mansour Hadi and a unified Yemen.

Hadi's government and the UAE are formally allies in a war against Yemen's Houthi rebels.

A coalition led by Saudi Arabia has been battling the Iran-aligned armed group for three years to restore Hadi to power.

Relations between Hadi and the UAE has soured due to the latter's expanding influence in southern Yemen.

Hadi has previously accused the UAE of behaving like an occupier, according to the Middle East Eye website.

The UAE's move to exert control over Socotra is seen by many as the latest move by the Arab Gulf state to spread its influence well beyond its borders.

The island is situated off the coast of Somaliland, where UAE has invested heavily in the commercial port of Berbera. </s> Angry protests have erupted on the Yemeni island of Socotra after the United Arab Emirates deployed four military aircraft and more than 100 troops to the famed UNESCO World Heritage Site.

Residents told Al Jazeera that the four Emirati aircraft arrived illegally on the island on Wednesday in an attempt to intimidate officials from the internationally recognised government who were making a rare visit to the archipelago.

Hundreds of Yemenis had come out to welcome Ahmed bin Daghr, Yemeni prime minister, and 10 of his ministers and to denounced the UAE's presence on the island.

Videos posted on social media showed protesters chanting slogans in support of President Abd-Rabbu Mansour Hadi and a unified Yemen.

Residents told Al Jazeera that the crowds were angry after reports emerged that Emirati forces had expelled Yemeni soldiers assigned to protect the main island's airport.

سقطرى تهتف لليمن بحضور ابن دغر.

شعب نبيل،يعاني ويهتف لوطنه.

بالله عليكم مثل هذا الجمهور ألا يستحق أن تكونوا معه؟

إنه يبحث عنكم.

عودوا إليه. pic.twitter.com/VqUzzW6pcL — Dr Mohammed Jumeh (@MJumeh) May 2, 2018

Located due east of the Horn of Africa in the Arabian Sea, the island of 60,000 people, which is known for its unique flora and fauna, has been administered by Yemen for much of the last two centuries.

But since the UAE entered Yemen's war in March 2015 as part of a Saudi-led coalition seeking to remove Houthi rebels, Abu Dhabi has exploited the security vacuum and tried to gain a foothold in the strategically placed island.

The UAE has confirmed carrying out military operations on Socotra, with local media reporting that the UAE had leased Socotra and the nearby Abd al-Kuri island for 99 years.

The flag of the UAE and images of Crown Prince Mohammed bin Zayed Al Nahyan adorn official buildings and busy thoroughfares.

According to Human Rights Watch, Abu Dhabi has financed and trained a network of militias that only answer to it, set up prisons, and created a security establishment parallel to Hadi's government.

Earlier this year, Yemen's tourism ministry warned that the UAE had tried to convince islanders "to vote on a referendum of self-determination", calling it a "dangerous step."

Andreas Krieg, an academic at King's College London, said the latest developments in Socotra were part of a much larger strategy to consolidate power in southern Yemen.

"The UAE see themselves, or want to see themselves in the future, as the link between the east and the west.

"It's very important for them to control trade links which mostly go through the suez canal and the Bab al-Mandeb Strait between Yemen and the Horn of Africa.

"What they've done is found an island that is very strategically located, acts as a quasi-aircraft carrier in the middle of the Indian ocean and where they can control traffic while giving favourable access to countries that are related to them." </s> The newspaper al-Quds al-Arabi has cited a Yemeni source as saying on conditions of anonymity that officials in Yemen's exiled government plan to turn to the UN Security Council in order to put an end to the United Arab Emirates (UAE)'s military presence on Socotra Island.

According to the source, more Yemeni government officials are "thinking of addressing the United Nations to get the UAE out of the Arab alliance."

The source described the UAE's actions as a "flagrant violation of Yemeni sovereignty," adding that Riyadh's pressure hinders the Yemeni government's drive to turn to the UN Security Council.

READ MORE: S Arabia, UAE Reportedly Trying to Soothe Tensions Amid Fresh Fighting in Yemen

The remarks came after Abu Dhabi deployed some 300 soldiers, along with tanks and artillery, to Socotra Island on April 30 without informing the Yemeni government-in-exile of President Abed Rabbo Mansour Hadi.

Yemeni Prime Minister Ahmed Bin called the UAE's takeover of Socotra an "unjustified" assault on Yemen's sovereignty, which he said "reflects the disagreement between the legitimate government and our brothers in the UAE, and at its core is a dispute over national sovereignty and who has the right to practice it."

The UAE's Foreign Ministry rejected the accusations, saying that Abu Dhabi "plays a parallel role in the Yemeni island of Socotra to maintain security and stability, support development projects, and help the people of the island."

READ MORE: Saudi-Led Strikes on Presidential Office in Yemen Kill 6, Injure 30 – Reports

Referring to the troops' deployment to Socotra, the ministry said that it "comes within the efforts of the Arab Coalition to support the legitimacy at this critical stage in the history of Yemen."

However, analysts pointed to the UAE starting to distance itself from Hadi, who is reportedly under house arrest in Riyadh, and carving out an area of influence in southern Yemen.

Socotra Island, located in the Arabian Sea and sometimes referred to as the "Galapagos of the Indian Ocean" and the "most alien-looking place on Earth" is listed by UNESCO as a world heritage site. </s> The United Arab Emirates has deployed its troops and seized key positions on the Indian Ocean island of Socotra.

There is public outrage on the island of Socotra in the Indian Ocean.

A UNESCO world heritage site, Socotra is Yemeni territory, whose residents do not want it to become part of the conflict in Yemen.

But on Thursday, the United Arab Emirates (UAE) deployed troops to the island, seizing strategic positions.

This angered the Yemeni government of President Abd-Rabbu Mansour Hadi, which says it wasn't informed of the move.

The UAE is part of the Saudi-led coalition fighting Houthi rebels in the country and is a former ally of Hadi, but splits have recently emerged.

What is driving Abu Dhabi's expansion in the region?

Andreas Krieg - assistant professor at the defence studies department at King's College London

Catherine Shakdam - Middle East commentator and researcher at Al Bayan Centre for Strategic Studies </s> Angry protests have erupted on the Yemeni island of Socotra after the United Arab Emirates deployed four military aircraft and more than 100 troops to the famed UNESCO World Heritage Site.

Residents told Al Jazeera that the four Emirati aircraft arrived illegally on the island on Wednesday in an attempt to intimidate officials from the internationally recognised government who were making a rare visit to the archipelago.

Hundreds of Yemenis had come out to welcome Ahmed bin Daghr, Yemeni prime minister, and 10 of his ministers and to denounced the UAE's presence on the island.

Videos posted on social media showed protesters chanting slogans in support of President Abd-Rabbu Mansour Hadi and a unified Yemen.

Residents told Al Jazeera that the crowds were angry after reports emerged that Emirati forces had expelled Yemeni soldiers assigned to protect the main island's airport.

Located due east of the Horn of Africa in the Arabian Sea, the island of 60,000 people, which is known for its unique flora and fauna, has been administered by Yemen for much of the last two centuries.

But since the UAE entered Yemen's war in March 2015 as part of a Saudi-led coalition seeking to remove Houthi rebels, Abu Dhabi has exploited the security vacuum and tried to gain a foothold in the strategically placed island.

The UAE has confirmed carrying out military operations on Socotra, with local media reporting that the UAE had leased Socotra and the nearby Abd al-Kuri island for 99 years.

The flag of the UAE and images of Crown Prince Mohammed bin Zayed Al Nahyan adorn official buildings and busy thoroughfares.

According to Human Rights Watch, Abu Dhabi has financed and trained a network of militias that only answer to it, set up prisons, and created a security establishment parallel to Hadi's government.

Earlier this year, Yemen's tourism ministry warned that the UAE had tried to convince islanders "to vote on a referendum of self-determination", calling it a "dangerous step."

Yemen's war has taken a huge toll, with more than 10,000 people killed, millions at risk of famine and a massive cholera outbreak.
The United Arab Emirates deploys troops on the Yemeni island of Socotra in the Arabian Sea, taking over key installations such as Socotra Airport from Yemeni soldiers. Yemeni Prime Minister Ahmed Obeid bin Daghr denounces the Emirati ground incursion and hundreds protest demanding their immediate withdrawal. Local media reports the UAE claims to have "leased" the island.