Zambian President Michael Sata, who was receiving medical treatment in London, died Tuesday, the Zambian government said.

Cabinet Secretary Roland Msiska said in a statement that Sata, who was 77, died at London's King Edward VII hospital shortly after 11 pm .

"It is with a very heavy heart that I address you today, to inform the nation that our beloved president and leader, His Excellency Mr. Michael Chilufya Sata, has passed on.

"President Sata's demise is deeply regretted. During this difficult period, I urge all of you to remain calm, united and peaceful," the statement said, reports The Guardian.

Msiska added that the Zambian President's wife, Christin Kaseba, and his son, Mulenga Sata were at his side when he passed away.

Two probable people who may succeed Sata are defense minister Edgar Lungu, who was appointed acting president when Sata traveled to London earlier this month, and Vice-President Guy Scott.

The Zambian constitution requires that the presidential election must be held within 90 days of a president's death.

Sata , who was called  "Mr. King Cobra" for his sharp - tongued remarks, was critical of Chinese investors in Zambian mines saying that they were exploitative. However, after taking charge as  President, he took a less critical stance against the investors, reports the Associated Press.

Among the many leaders who paid tributes to Sata were the Prime Minister of Uganda Ruhakana Rugunda, and the President of Somalia, Hassan Sheikh Mohamoud,.

British foreign secretary, Philip Hammond, also paid tribute to Sata.

"[Sata] 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, " Hammond said in a statement, reports The Guardian.