PORT LOUIS (Reuters) - The African Union on Friday called on Britain to withdraw from the Chagos Islands and end its “continued colonial administration” there after a U.N. deadline for it to do so expired.

The Chagos Islands belong to the Indian Ocean island nation of Mauritius, according to an advisory opinion from the top United Nations court issued in February. The U.N. General Assembly voted in May in favor of Britain returning the islands to Mauritius and set a deadline for Nov. 22.

The African Union urged Britain to comply with the U.N. resolution and reiterated the AU’s support “for a complete decolonisation” of the Chagos Islands.

Britain does not recognize Mauritius’ sovereignty claim.

“The UK has no doubt as to our sovereignty over the British Indian Ocean Territory (BIOT), which has been under continuous British sovereignty since 1814,” Britain’s Foreign Office said in a statement on Nov. 5.

Around 200 protesters gathered outside the British High Commission in Port Louis, the capital of Mauritius, on Friday. They demanded Britain cede the Chagos Islands to Mauritius and said they wanted to return to the archipelago where they were born.

A group supporting the rights of people indigenous to the Chagos Islands said they were considering options for filing a case against Britain at the International Criminal Court.

Slideshow ( 2 images )

“We have to look at different avenues given that the UK is not complying with the decision of the United Nations,” Olivier Bancoult, who was born on one of the islands of the archipelago and is leader of the Chagossian Refugee Group, told Reuters.

Mauritius Prime Minister Pravind Kumar Jugnauth said that Britain’s refusal to give up control of the islands was a violation of international law.

“The United Kingdom cannot profess to be a champion of the rule of law and human rights whilst maintaining an illegal colonial administration,” he told parliament on Thursday.

The only inhabited island of the Indian Ocean archipelago is home to the Diego Garcia U.S. military base, rented out by Britain, and a bomber base for the Air Force.

Mauritius will continue to allow the United States to operate the base even if it resumed control over the islands, Jugnauth said in parliament on Thursday.

“Mauritius has stated on various occasions that it fully recognizes the importance of the military base in Diego Garcia and will take no action that will impede its continued operation,” he said.