The United States called Sunday for the peaceful and transparent resolution of any election disputes in the Democratic Republic of Congo after President Felix Tshisekedi was declared winner of a second term in the turbulent nation.

Provisional results showed Tshisekedi had won 73 percent of the vote, which opposition leaders have already dismissed as a "sham."

The United States is following the process "closely," a State Department spokesperson said, stopping short of immediately congratulating Tshisekedi.

"Any election disputes should be resolved peacefully and in accordance with Congolese electoral law," the spokesperson continued. "We call on the relevant authorities to ensure any complaints are handled in a fair and transparent manner."

The Democratic Republic of Congo's Constitutional Court is expected to confirm the provisional results on 10 January . 

Moise Katumbi — a wealthy businessman, football club owner, and former provincial governor — was the election runner-up with about 18 percent.

He and eight other opposition candidates on Sunday signed a declaration rejecting the results and calling for a re-run.

Post-election tensions have been common in the poor but mineral-rich country. 

Analysts said Tshisekedi's vote tally was well beyond expectations.

Over 40 million people out of the 100 million inhabitants of the huge country were registered to vote on December 20 for president, as well as for national and regional lawmakers and municipal councilors.

Voting was officially extended by a day to account for problems, and continued for days afterward in remote areas, according to observers.