In the final tally, Hichilema secured 2,810,777 votes while Lungu was in second place with 1,814,201 votes, out of seven million registered voters in the African nation.

"I therefore declare that the said Hichilema to be president of Zambia," said electoral commission chairman, Esau Chulu, to a packed results centre in the capital Lusaka on Monday.

The massive win meant Hichilema does not have to contest any second round run-offs after meeting the constitutional 50.1 per cent threshold for an outright winner.

The election has been marred by sporadic violence and Hichilema would face a daunting task turning around the economic fortunes of one of the world's poorest countries.

Lungu said on Saturday the election was "not free and fair" after incidents of violence against ruling Patriotic Front party agents in three provinces, and the party was consulting on its next course of action.

Officials from Hichilema's United Party for National Development party dismissed Lungu's statement as emanating from people "trying to throw out the entire election just to cling on to their jobs".

If Lungu wants to settle a dispute or nullify elections, he must approach the Constitutional Court within seven days to lodge a complaint after a winner is announced.

Hichilema, who has been leading a mainly two-horse race since the first results were announced on Saturday, seeks to reverse a narrow loss in the 2016 presidential election against Lungu, 64, who was seeking a second five-year term.

The COVID-19 pandemic, youth unemployment, falling copper prices from Zambia's mainstay export commodity and unsustainable fiscal policies have led to growing public discontent with Lungu.

Australian Associated Press