The Democratic Republic of Congo's Constitutional Court has confirmed Felix Tshisekedi's landslide re-election in December polls - paving the way for him to serve another five years as president of the mineral-rich country.

The court on Tuesday rejected two legal challenges to the provisional results of last month's contested 20 December presidential, legislative, regional and local elections.

Nine opposition leaders signed a declaration declaring the polls, in which Tshisekedi got 73.47 percent of the vote, a "sham" - and calling for a re-run.

More than 40 million of the DRC's 100 million inhabitants were registered to vote.

Logistical issues

Polling was extended by a day to account for problems, and continued for days afterwards in remote areas amid reports of widespread irregularities.

Logistical mishaps, a last-minute extension of voting and a murky tabulation process have stoked ongoing disputes that threaten to further destabilise the poverty-stricken nation, which is also the world's top producer of cobalt and other prized industrial commodities.

The final figures announced by the court on Tuesday differed only slightly from provisional results that election officials had already made public.

Following Tshisekedi is Moise Katumbi, a former governor of the central Katanga region, with 18.08 percent.

A Katumbi spokesman accused the court of covering up cheating and fraud with a "legal varnish".

Both the government and the electoral commission have insisted the elections were free and fair.

Church leaders, who deployed their own election observers, noted numerous cases of irregularities and urged an investigation, but fell short of declaring the vote fraudulent.

Congo's former coloniser Belgium congratulated Tshisekedi for his victory and encouraged the electoral commission to pursue investigations into the election's irregularities.

(with newswires)