LONDON (BLOOMBERG) - The one-time inhabitants of the remote Chagos Islands in the Indian Ocean said they will challenge the United Kingdom's refusal to let them resettle on the archipelago in Britain's Supreme Court.

The United Nations and the African Union have said the UK should withdraw from its last African colony.

A case brought by the activists challenging UK government policy to refuse the Chagossians' return and provide financial support instead was dismissed on Thursday (July 30) by the UK Court of Appeals.

The case is one of a long series of legal challenges brought by Mr Olivier Bancoult, the head of the Chagos Refugee Group who was deported from the territory as a child.

The UK is under international pressure to give up the archipelago, which is home to a strategically important US Air Force base on its biggest island, Diego Garcia.

Since purchasing the area from its then colony Mauritius in 1965, the UK has kept all other islands free of inhabitants by declaring the area a protected marine reserve in 2010.

"We're very disappointed with the latest ruling and so are all the people who believe in the fundamentals of human rights," Mr Bancoult said by phone from Port Louis, the capital of Mauritius.

"We will challenge it at the level of the Supreme Court of the UK and even the European Human Rights Court."

Mauritius has put the archipelago on its national map since the International Court of Justice ruled last year that the 1965 takeover of the islands had been unlawful.

The UN General Assembly affirmed the ruling in May 2019 and set a six-month deadline for the UK to withdraw.

The African Union has urged the UK to comply with the UN resolution.

The UK has said that the manner in which the Chagossians were removed from the islands in the 1960s and 1970s was wrong, but opposes their resettlement on security grounds.