The Zambian government says vice president Guy Scott, a white Zambian of Scottish descent, will become acting president following the death of Michael Sata.

Mr Scott will lead the southern African nation until elections are held within 90 days.

He is the first white leader of an African nation since FW de Klerk, the last president of apartheid, the South African system of white racist rule that ended in 1994.

Zambia's defence minister Edgar Lungu announced the appointment of Mr Scott, who was born in Livingstone, Zambia. His father was from Glasgow and emigrated to Northern Rhodesia in 1927.

President Sata died shortly after 11pm yesterday at London's King Edward VII hospital, where he was being treated, cabinet secretary Roland Msiska said in a statement.

Mr Sata's wife, Christine Kaseba, and his son, Mulenga Sata, were at the 77-year-old president's side when he died, Mr Msiska said.

Mulenga Sata is the mayor of the Zambian capital, Lusaka.

"I urge all of you to remain calm, united and peaceful during this very difficult period," Mr Msiska said in an appeal to Zambians.

Mr Scott's appointment as vice president in 2011 caused a stir in the country. He had previously held the post of agriculture minister and has also worked in Zambia's finance ministry.

Rumours that Mr Sata was seriously ill had gripped Zambia since the leader largely dropped out of public view months ago, and opposition groups criticised the government for declining to release details about his medical condition.

Since June, the president has made only a few brief appearances and missed a number of summits, including a scheduled speech at the UN General Assembly in New York.

On September 19, he delivered an address at the opening of parliament in Lusaka, poking fun at speculation about his failing health.

"I haven't died yet," the Zambian president said at the time.

On Friday, he missed national celebrations marking the 50th anniversary of Zambian independence.

Earlier this year, Mr Sata travelled to Israel on what officials called a "working holiday", though there was widespread speculation that he went there for medical treatment.

On October 20, the Zambian government said Mr Sata had left for a "medical check-up abroad", without specifying that he had gone to London.

Mr Scott, 70, has said he has no presidential ambitions, and analysts say he cannot become a fully empowered president because his parents were born outside Zambia.

"Dr Scott will act as president of the republic of Zambia until the country goes for a presidential by-election," said Mr Lungu, who is secretary general of the ruling Patriotic Front party.

"The government remains intact and so does the Patriotic Front as a party," he added.

Zambia had already declared today to be a national day of mourning for 26 people, 23 of them schoolchildren, who died last week when a crowded boat capsized on Lake Kariba, near the border with Zimbabwe.

The children were on their way to a ceremony marking Zambia's 50th anniversary of independence from Britain. Mr Sata was unable to preside over the national celebrations because he was in the London hospital.

In a national radio address, Mr Scott said: "Elections for the office of president will take place within 90 days. In the interim, I am the acting president.

"The period of national mourning started today. We will miss our beloved president and commander."