Five opposition presidential candidates informed the governor of Kinshasa in a letter published Saturday of their intention to organize the march.
With definitive results still not announced, the government said the protests would be disruptive.
"Tomorrow's demonstrations are intended to undermine the electoral process — the government of the republic cannot accept this," Interior Minister Peter Kazadi told journalists. "I can assure you that there will be no such march."
The opposition leaders who signed the letter include Martin Fayulu — who claimed he won last elections in 2018 — and Denis Mukwege, the Nobel Peace Prize winner for his work with victims of wartime sexual violence.
They denounced the election as a "sham."
"We will protest against the irregularities observed during voting," they wrote.
Moise Katumbi, another candidate and former governor of the south-east Katanga region, called for the elections to be annulled.
Almost 44 million voters, out of about 100 million inhabitants of the massive country, were eligible to elect their president, national and regional lawmakers and municipal councils in last Wednesday ballots.
Due to numerous logistical problems, the voting was officially extended by a day, and even lasted until Christmas Day in some remote areas.
The opposition claimed there was "total chaos."
Extremely partial results released by the electoral commission show incumbent President Felix Tshisekedi well ahead, with 80% of the some 1.8 million ballots counted so far.
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