A Congolese opposition party and former rebel group on Tuesday denounced what it called widespread fraud in the country's historic elections in a protest that heralded a bitter political dispute over the polls.
The RCD party of presidential contender Azarias Ruberwa said unless its allegations of "systematic fraud" were cleared up it would contest the election results, due by August 20.
The complaint posed an early challenge to Congolese electoral authorities and the United Nations which on Sunday held the country's first free multi-party polls in 40 years under the protection of 17,000 UN peacekeepers.
Millions of Congolese turned out to vote across the vast, former Belgian colony in what world leaders hailed as generally exemplary, peaceful elections. Counting was under way and President Joseph Kabila was widely seen as favourite to win.
But many analysts have expressed fears "bad losers", especially rivals of Kabila who once fought against him as rebels during a 1998-2003 war, may try to spoil the electoral process through protests and violence.
Ruberwa's RCD (Congolese Rally for Democracy) party, a former Rwandan-backed rebel group, on Tuesday said there were numerous poll irregularities which could distort the vote.
"I declare that the massive nature of the fraud and irregularities could stain the results," Ruberwa told a news conference in Kinshasa. In its complaint, the RCD cited cases of ballot stuffing, biased election officials and duplication of voting cards and accused Kabila's party of buying votes with money.