He retired from politics in 2021 after a crushing defeat in the presidential election.

After six years in power, he left the country with heavy debts and an unstable economy.

But now Lungu is looking to capitalize on growing discontent with his successor, Hakainde Hichilema.

His return had been awaited for a long time, but this was the first official announcement.

"I am ready to fight from the front, not from the back, defending democracy. Those who are ready for this fight, please come with me, I am ready for anything," Mr. Lungu told supporters on Saturday. spoke at a memorial service for former president and leader of his Patriotic Front (PF) party, Michael Sata, who died in office in 2014.

Since Mr. Lungu lost power two years ago, there has been a dispute within the FN over who should lead the party, which has ended up on trial. The arrival of Mr. Lungu may well increase tensions and prolong the legal battle, as there is now another person, Miles Sampa, who claims to have been elected president of the FN at a recent meeting. 

Some, including the former president, accuse the government of fomenting discord, which it denies.

Mr. Lungu "enjoys a constitutional and democratic right to participate in the political sphere of our country, and if he so wishes, he is welcome back in the political arena," Information Minister Cornelius Mwitwa told Zambian public broadcaster ZNBC.

Mr. Hichilema won the 2021 election, his sixth point as president, with 59% of the vote in the hope that he would solve the country's economic problems.

But it takes a lot of time for these high expectations to be met, and patience is running out.

The president managed to conclude an agreement on financial assistance to the copper-rich country with the International Monetary Fund. He also managed to restructure loan agreements with Chinese and other lenders. 

Mr. Hichilema argues that he inherited a country experiencing deep economic problems, in which the critical mining sector struggled.

But the average consumer is faced with very high prices for basic food and fuel, making life difficult for many and leading to disillusionment with political leadership.

This week, the government was also criticized for "growing intolerance of dissent" by 13 leading civil society organizations. In a joint statement, they said the country was "shrinking the space for freedom of expression and assembly."

In the past, the president has said that he respects human rights and does not interfere in police activities.

His Saturday runs with ordinary members of the public and PF supporters attracted a lot of attention. The former president was ordered to request police permission for future runs.