The new president of the Democratic Republic of Congo, Félix Tshisekedi, has been sworn into office.
He told supporters at a ceremony at the presidential palace in Kinshasa he wanted to build a “reconciled Congo”.
Mr Tshisekedi was briefly taken ill before resuming his speech.
He is taking over from Joseph Kabila in the first peaceful transfer of power in the country in nearly 60 years, though many still dispute his victory in last month’s presidential election.
Kenya’s President Uhuru Kenyatta was the only African head of state, out of 17 invited, to watch the ceremony.
Numerous sources say his opponent Martin Fayulu won a landslide victory and has been denied office by a backroom deal between Mr Kabila and Mr Tshisekedi.
The influential Catholic Church, which deployed election observers on voting day, said the official data did not match its own numbers.
Mr Fayulu’s appeal to the Constitutional Court for a vote re-count was rejected, and critics say the body is too close to outgoing President Kabila and lacks independence.
Mr Tshisekedi had to cut short his inaugural address on Thursday after feeling faint. But he returned to the podium, saying he was exhausted from the long presidential campaign and the emotion of the day.
“We want to build a strong Congo, turned toward development in peace and security – a Congo for all in which everyone has a place,” he told the crowd.
Many people there believe the handover does show the DR Congo is becoming more democratic, the BBC’s Gaïus Kowene in Kinshasa reports.
Addressing the nation on Wednesday, Mr Kabila called on Congolese citizens to support his successor, who he said could call on him for advice at any time.
The new president is mostly known for being the son of the late veteran opposition leader Etienne Tshisekedi, who was regarded as one of DR Congo’s most important pro-democracy advocates.
The Union for Democracy and Social Progress (UDPS) party President Tshisekedi leads was founded in 1982 by his father, who turned it into the largest opposition party.
But President Tshisekedi, 55, insists he is not trying to rival his father.
Why DR Congo matters:
A presidency without power?
Analysis: Fergal Keane, BBC Africa editor
Félix Tshisekedi comes to the presidency with little weight of expectation from beyond his own support base.
What was supposed to be the first democratic transfer of power since independence in 1960 looks tainted with strong suspicions that the outgoing president, Joseph Kabila, intends to exert control from behind the scenes.
Mr Tshisekedi’s challenges are immense. His UDPS did poorly in the elections, so he lacks the firm parliamentary base which might give him the means to assert his independence as president.
The senior echelons of the army and police are all appointees of the old regime. Removing them would be a significant sign that the new president means to be independent.
But would he risk challenging Joseph Kabila? It is highly unlikely. Félix Tshisekedi may find he has been handed the responsibility of the presidency but with little of the power.