The African Union continental body issued a surprise last-minute demand late Thursday for Congo's government to suspend the announcement of final results of the disputed presidential election, citing "serious doubts".

DRC's constitutional court is poised to rule as early as Friday on a challenge filed by the election's declared runner-up. Martin Fayulu has requested a recount, alleging fraud. Upholding the results could spark violence in a country hoping for its first peaceful, democratic transfer of power since independence in 1960.

The AU statement said heads of state and government agreed to "urgently dispatch" a high-level delegation to Congo to find "a way out of the post-electoral crisis" in the vast Central African nation rich in the minerals key to smartphones and electric cars around the world.

"This is truly incredible," tweeted Jason Stearns, director of the DRC Research Group at New York University. "Usually, the African Union defers to the subregion ... in this case they departed dramatically."

DRC faces the extraordinary situation of an election allegedly rigged in favor of the opposition. There was no immediate government comment.

Fayulu accuses the administration of outgoing President Joseph Kabila of falsifying the results to declare opposition leader Felix Tshisekedi the winner after the ruling party candidate did poorly. Fayulu has cited figures compiled by the influential Catholic Church's 40 000 election observers that found he won 61% of the vote.