The UK has been widely criticised after missing a UN deadline to hand over control of the Chagos Islands to Mauritius.
As the due date passed on Friday, the African Union called for a "complete decolonisation" of the islands and expressed "deep concern" for the missed deadline.
It came a day after Mauritius Prime Minister Pravind Kumar Jugnauth told parliament the UK had violated human rights and international law by "maintaining an illegal colonial administration".
According to a UN advisory ruling in February, the UK acted unlawfully in its separation of the Chagos Archipelago from Mauritius in the 1960s.
In May, the UN General Assembly then voted in favour of the UK relinquishing control of the islands and enacted a six-month deadline.
But the UK government, which calls the islands the British Indian Ocean Territory, has previously rejected foreign claims of sovereignty.
In a statement in early November, it said: "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."
Euronews has reached out to the UK's foreign office for comment on Friday's expired deadline.
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It comes as a particularly controversial case due to the UK's control of the islands after Mauritius gained independence in 1968 leading to the displacement of thousands of islanders.
Their displacements made way for a US military base on the archipelago's largest island, Diego Garcia.
Chagos Support UK, an association of volunteers speaking out for displaced Chagossians, said on Friday the community was "united in demanding their fundamental right to live on their islands and recompense for over fifty years of abuse and neglect."
It added: "The UN General Assembly and International Court of Justice (ICJ) verdict highlighted the vicious treatment of Chagossians to the wider world. Chagossians can not wait any longer."
Meanwhile, other experts were also vocal in their criticisms of the UK's lack of response.
Mark Curtis, a foreign policy and international development expert, said the UK was acting the part of "a rogue state" for appearing to ignore the UN's deadline.
He added: "Nothing sensationalist about this, it's a statement of fact."
Former British ambassador to Uzbekistan Craig Murray said the UK had shunned the rulings.
He said: "You can vote not to be a criminal rogue state", in reference to the upcoming general election in December.