- Emery Makumeno in Kinshasa & Joseph Winter in London
- BBC News
President Félix Tshisekedi has been declared victorious in the Democratic Republic of Congo's election, which has been condemned as “brutal” by several opposition candidates calling for a re-run.
The president won about 73% of the vote, while his nearest rival, Moise Katumbi, got 18%, officials said.
The December 20 election was marred by widespread logistical problems.
It had to be extended to a second day in some parts of the vast country.
According to the observer group, two-thirds of polling stations opened late, while 30% of voting machines did not work on the first day of voting.
Hundreds of thousands of people waited for hours before casting their ballots, and some even gave up and went home.
The opposition said the problems were part of a planned scheme to allow the results to be rigged in favor of the 60-year-old Mr Shisegedi.
Several key contestants have called for protests after the results were announced.
In a joint statement on Sunday, “We call upon our people to come to the streets en masse after the declaration of electoral fraud.
The army has been deployed in various parts of the capital Kinshasa to prevent rioting, while Mr Tshisekedi's supporters have taken to the streets to celebrate.
The Election Commission chief had earlier said that opposition candidates wanted fresh elections because “they know they lost…they are bad losers”.
Election chief Denis Kadima acknowledged some irregularities but insisted the results reflected the will of the Congolese people.
President Tshisekedi will be sworn in for a second term on January 20.
The president, son of veteran opposition leader Etienne Tshisekedi, was first elected in 2019.
It followed a poll in which some observers, including the influential Catholic Church, said former oil executive Martin Faiulu had won. In this election he got 5% votes and came third.
None of the other 16 candidates received more than 1% of the vote.
Mr Khatima said 43% of the 41 million registered voters had cast their votes.
It is unclear whether any of the 18 opposition candidates will challenge the results in court. Mr Katumbi has already said that the courts are not independent and therefore have no value.
The Constitutional Court has 10 days to hear any legal challenges before it announces its final decision on 10 January 2024.
DR Congo is roughly four times the size of France, but lacks basic infrastructure. Even some of its major cities are not connected by road.
Two-thirds of the country's 100 million people live below the poverty line, earning $2.15 (£1.70) a day or less.
Voters also chose parliamentary, provincial and municipal representatives, with a total of 100,000 candidates.
During the campaign, Mr Tshisekedi repeatedly lashed out at Rwandan President Paul Kagame, accusing him of supporting the M23 rebel group that has seized territory in the east of the country. Rwanda has repeatedly denied the allegations.
In his last election rally, Mr Tshisekedi vowed to declare war on Rwanda, although observers dismissed this as rhetoric intended to stoke nationalist sentiment.
Due to the three decades of fighting in the east, elections have not been held in those areas.
Dozens of armed groups are fighting for control of parts of the region, home to the country's largest mineral reserves.
It also includes vast reserves of cobalt, a key component of many lithium batteries seen as essential to a future free of fossil fuels.