Foreign Secretary Philip Hammond has led tributes to Zambian president Michael Sata, who died yesterday in a London hospital.
The 77-year-old African leader died in the private King Edward VII's hospital, Zambian cabinet secretary Roland Msiska said in a televised address.
Mr Sata's wife, Christine Kaseba-Sata and his son, Mulenga Sata, the mayor of the country's capital Lusaka, were at his bedside when he died, Dr Msiska added.
Mr Hammond said he was saddened to hear of Mr Sata's death, adding: "He played a commanding role in the public life of his country over three decades, as governor of Lusaka, as the holder of several ministerial positions in the 1990s, as the main opposition leader, and finally as president.
"I would like to offer my condolences to his family and to the Zambian people at this time."
Announcing Mr Sata's death, Dr Msiska urged the people of Zambia to "remain calm, united and peaceful during this very difficult period".
Mr Sata was elected president in 2011, when he defeated incumbent Rupiah Banda.
Fears over Mr Sata's health began mounting in June when the president disappeared from public view, according to reports.
Since then he 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 last month.
On Friday he missed national celebrations marking Zambia's 50th anniversary of its independence.