The constitutional court has seven days to consider the challenge.

Fayulu has alleged a backroom deal between the declared winner, opposition leader Felix Tshisekedi, and President Joseph Kabila.

He told reporters, "you can't manufacture results behind closed doors".

Fayulu's coalition asserts he won 61 per cent of the vote according to the Catholic Church's 40,000 election observers across the country.

Congo's electoral commission says he received 34 per cent and Tshisekedi 38 per cent.

The commission's president has said there are two options: The official results are accepted or the election is annulled.

Tshisekedi's camp denies that there was any deal with Kabila and says meetings it held with the president's representatives after the election were meant solely to ensure a peaceful transfer of power.

In a tweet on Saturday, Fayulu wrote that the results "were invented out of whole cloth".

"I demand a hand recount of all votes for the three elections (presidential, national legislative and provincial)," he wrote.

The disputed outcome threatens to reawaken violence in the huge and tumultuous central African country where millions have died during civil wars since the 1990s.

Security forces killed dozens who protested at Kabila's refusal to step down when his official mandate expired in 2016.

Australian Associated Press