Democratic Republic of Congo President Joseph Kabila says there is no doubting the credibility of his re-election.

During a news conference in Kinshasa Monday, Mr. Kabila acknowledged that mistakes were made during last month's poll, but he rejected the conclusion of the Carter Center that it had been “mismanaged” and lacked credibility.

The U.S.-based election monitor said that polling stations in Kabila strongholds reported “impossibly” high turnouts, and that many ballots in his rival's strongholds were reported lost.

Congo's electoral commission declared Mr. Kabila the winner of the poll on Friday. Shortly after, challenger Etienne Tshisekedi rejected the results and declared himself president.

President Kabila on Monday denied there was a crisis in Congo and urged Mr. Tshisekedi to — in his words — “make good use of the justice system” if he disagrees with the election result.

Violent protests and looting left four people dead in Kinshasa following the announcement of the election results, but a heavy mobilization of police and security personnel has since restored a tense calm to the city.

Mr. Tshisekedi has called on supporters to remain calm and await further instructions. He has also expressed hope the international community will help mediate the dispute.

The presidential and legislative polls two weeks ago were only the second free elections since the African nation was torn apart by several years of warfare that ended in 2003.