Congo's top court confirmed Felix Tshisekedi's contested presidential election win on Sunday, drawing a rebuke from the second-placed candidate who declared himself leader and called for demonstrations.
As Tshisekedi's supporters celebrated in the streets of Democratic Republic of Congo's capital, runner-up Martin Fayulu said the ruling had opened the way to a "constitutional coup d'etat," raising fears of more violence.
Last month's delayed vote was meant to mark the first democratic transfer of power in the Central African country.
But monitors have pointed to major flaws. Unrest over the vote has already killed 34 people, wounded 59 and led to 241 "arbitrary arrests" in the past week, according to the UN human rights office.
Early Sunday, the Constitutional Court ruled that a legal challenge to the result filed by Fayulu was inadmissible. "Felix Tshisekedi will become the fifth president of the republic," government spokesman Lambert Mende said as he welcomed the judgement.
Fayulu issued statements dismissing the ruling. "The constitutional court has just confirmed that it serves a dictatorial regime ... by validating false results, (and enabling) a constitutional coup d'etat," he said in one.
"I am now considering myself as the sole legitimate President of the Democratic Republic of Congo," he added in another statement. He called for people to mount peaceful demonstrations across the country.
Fayulu says Tshisekedi and outgoing President Joseph Kabila made a deal to cheat him out of a more than 60-per cent win - an accusation they both dismiss.
The provisional results, announced on Jan 10, showed Tshisekedi winning with a slim margin over Fayulu. Kabila's officially favoured candidate Emmanuel Ramazani Shadary came in a distant third.
In a speech, Tshisekedi welcomed the victory and said he would seek to mend divisions in the country.
"This is the end of one fight and the start of another in which I will enlist all the Congolese people: a fight for well-being, for a Congo that wins," he said. "The Congo we will build will not be a Congo of hate, tribalism and division."
Independent monitors flagged major problems, including faulty voting machines and polling stations where many were unable to vote. The Catholic Church, which had a 40,000-strong team of observers, denounced the provisional result.
A tally from the church reviewed by Reuters from about 70 percent of polling stations suggested a victory of 62 percent for Fayulu, a former Exxon Mobil country manager. Tshisekedi and Ramazani were virtually neck-and-neck second place with 16.93 percent and 16.88 percent, respectively.