Zambian President Michael Sata has died at the age of 77 after receiving treatment for an undisclosed illness, the government says.

President Sata, who was being treated in the UK, died in London's King Edward VII hospital on Tuesday night.

Media said that he died after “a sudden onset [of] heightened heart rate.”

It is not immediately clear who will succeed the president. The issue may be decided by the Zambian cabinet which meets on Wednesday morning.

“It is with a heavy heart that I announce the passing on of our beloved president,” cabinet secretary Roland Msiska said.

His death comes just days after Zambia celebrated the 50th anniversary of independence from the UK.

Earlier this month reports in Zambia said that President Sata had gone abroad for a medical check-up amid persistent speculation that he was seriously ill.

After he left the country, Defence Minister Edgar Lungu was named as acting president.

Vice-President Guy Scott has regularly stood in for the president at official events. But he is of Scottish descent and his parents were not born in Zambia, so he may fall foul of a constitutional clause on parentage which would nullify his candidacy.

Known as “King Cobra” for his venomous tongue, Mr Sata was elected Zambia’s president in September 2011, defeating the then incumbent Rupiah Banda whose party had been in power for 20 years.

He was rarely seen in public since returning from the UN General Assembly last month, where he failed to make a scheduled speech.

•Adapted from a BBC report. Photo shows late Zambian President Michael Sata alias King Cobra.