Zambia's former President Edgar Lungu has died at the age of 68, his party has said in a statement.

He had "been receiving specialized treatment in South Africa" for an undisclosed illness, the Patriotic Front (PF) added.

Lungu led Zambia for six years from 2015, losing the 2021 election to the current President Hakainde Hichilema by a large margin.

After that defeat he stepped back from politics but later returned to the fray. He had ambitions to vie for the presidency again but at the end of last year the Constitutional Court barred him from running, ruling that he had already served the maximum two terms allowed by law.

In a short video, Lungu's daughter Tasila said that the former head of state, who had been "under medical supervision in recent weeks", died at a clinic in South Africa's capital, Pretoria, at 06:00 (04:00 GMT) on Thursday.

"In this moment of grief, we invoke the spirit of 'One Zambia, One Nation' - the timeless creed that guided President Lungu's service to our country," she added in an emotional statement.

Lungu first became president in January 2015 after winning a special presidential election triggered by the death of Michael Sata.

After completing Sata's term, he won a further five years in power in 2016 taking just over 50% of the vote.

But after six years at the helm, Lungu was blamed for a struggling economy and high unemployment. He lost in 2021 by close to a million votes with Hichilema tapping into widespread dissatisfaction among the electorate.

He said he was retiring in the aftermath of the vote, but returned to frontline politics in 2023 as his successor's popularity waned.

"I am ready to fight from the front, not from the rear, in defence of democracy. Those who are ready for this fight, please come along with me, I am ready for anything," Mr Lungu told supporters at the time.

Lungu was a lawyer by training but enjoyed a meteoric rise in politics after winning a seat in parliament as a PF MP in 2011.

He entered government as deputy minister in the vice-president's office in that year and rose to become minister of home affairs in just over 12 months.

He later became minister of defence and then justice. A close friend described Lungu as a "good foot-soldier, lawyer and politician, father, husband and grandparent".

Born on 11 November 1956, Lungu graduated with a law degree from the University of Zambia in 1981. He also underwent military training at the then Miltez army college in Kabwe.

He later worked at Andre Masiye and Company Advocates, Barclays Bank, and Zambia Consolidated Copper Mines.