The African Union has urged candidates in this week's Congolese elections to accept the results, one day after four presidential hopefuls called for the results to be annulled.

Voting for the presidential and legislative elections began Monday and has stretched into Wednesday in some areas because of a shortage of ballots.

In a joint statement Wednesday, the AU and four other African organizations observing the polls welcomed what they called the successful holding of the elections.

The organizations noted logistical challenges facing Congolese officials, and expressed regret for “isolated acts of violence.” But they appealed to all stakeholders to accept the election outcome and pursue any disputes in the courts.

On Tuesday, four presidential candidates, including Vital Kamerhe, who is considered one of the main challengers to incumbent Joseph Kabila, called for the vote to be annulled, citing fraud.

The electoral commission rejected a claim from Mr. Kamerhe that some ballots were pre-marked for Mr. Kabila.

Vote counting is underway and results are expected before December 6, when President Kabila's term ends.

This is the second time the Democratic Republic of Congo has held multi-party polls since the end of a brutal civil war eight years ago.

Parts of the country remained wracked by violence, especially in the northeast province of North Kivu.