“I now consider myself the only legitimate president,” he added.

Congo went to the polls in December in what was intended to be the country’s first democratic handover of power in the 59 years since it gained independence from Belgium. For the past 21 years, the country has been led by the Kabila family, first by Laurent-Désiré Kabila and then by his son Joseph Kabila.

But challenges were filed to the court, including by Mr. Fayulu, who said the result was announced only after Mr. Tshisekedi and Joseph Kabila, the outgoing president, came to a power-sharing agreement. The two have denied any such deal.

Fears of violent protest and a crackdown by the government have gripped the nation since the election. The government went as far as cutting internet and text messaging services in an attempt to maintain order in the weeks after the polls. Service was restored on Saturday night.

On Saturday, hundreds of supporters of Mr. Tshisekedi gathered in the capital, Kinshasa, to protest the challenge to his win. During a Friday news conference, Mr. Fayulu urged calm ahead of the results.