Martin Fayulu, the runner-up in the Democratic Republic of the Congo's presidential election, has filed an appeal against the result of the election.
On Thursday, the country’s electoral commission declared Felix Tshisekedi as the winner of the December 30 election.
On Friday, Fayulu's legal team appealed to the Constitutional Court to annul the announced result.
"The request seeks the annulment of the result declaring Felix Tshisekedi president," Fayulu's lawyer Feli Ekombe told reporters on Saturday.
The presidential election, which was intended to be Congo's first democratic transfer of power in six decades, is now threatening to reawaken violence in the huge and tumultuous nation, where millions have died during civil wars since the 1990s.
Despite pre-election polls predicting a landslide victory for Fayulu, the national election board (CENI) declared Tshisekedi as the winner of the vote.
Fayulu's supporters, who took part in a protest rally in Kinshasa on Friday to contest the election result, claim the businessman-turned-politician won the vote.
The tally by Fayulu's camp showed that he won 62 percent of the votes, with Tshisekedi taking only 19 percent of the ballots.
Fayulu's supporters say authorities rigged the result in a deal to protect members of President Joseph Kabila's outgoing administration and maintain his influence over security forces.
The influential Catholic Church has also rejected the official result based on tallies by its 40,000-strong observer team. France and former colonial power Belgium also expressed doubts. Russia and China, however, called on foreign countries to stay out of the dispute.
Fayulu urges supporters to 'rise up'
Fayulu has asked his supporters to take action and defend his votes in the presidential election.
"When you know you are in the right, you are not allowed to remain home," Fayulu said, urging supporters to "rise up."
Fayulu's camp has asked the CENI electoral authority to publish results from every polling station.
Kabila, who took over from his assassinated father Laurent in 2001, is stepping down after 18 years in office. He has promised DR Congo's first orderly transfer of power since it gained independence from Belgium in 1960.