Regional powers hailed Felix Tshisekedi on Sunday as Democratic Republic of Congo's incoming president despite claims by his opponents of an election stitch-up and the EU and African Union warning of doubts over the result.

Announcing the final results of the much-delayed poll, the Democratic Republic of Congo's Constitutional Court threw out a challenge by runner-up Martin Fayulu in an overnight declaration.

It declared Tshisekedi the winner, paving the way for him to take over from the country's longtime leader Joseph Kabila, 47.

The election dispute has raised fears of fresh bloodshed in the vast and volatile central African nation.

An EU spokeswoman pleaded for all sides to refrain from "any action that could lead to violence".

"As expressed by the AU (African Union) high level consultative meeting on Thursday in Addis, doubts remain regarding the conformity of the result," she added.

The chairman of the African Union (AU), Rwandan President Paul Kagame, was due in Kinshasa on Monday after the AU questioned the election results.

But the 16-nation Southern African Development Community congratulated Tshisekedi on Sunday for being declared president-elect and called for a peaceful handover of power.