Angola's leading opposition party has filed a legal complaint challenging the integrity of last week's election, which saw the ruling MPLA party win by a narrow majority.
"The complaint about the final results was filed with the (national electoral commission) today," Faustino Mumbika, national secretary of the National Union for the Total Independence of Angola (UNITA), told AFP.
The 24 August elections were the most hotly contested in the oil-rich country since its first multi-party vote in 1992.
Results declared on Monday placed the Movement for the Liberation of Angola (MPLA) as the winner with 51.17 percent of the vote, securing a second term for President Joao Lourenco, 68.
UNITA made significant gains, earning 43.95 percent of the vote, up from 26.67 percent in the previous election in 2017.
But in a late-night video address, UNITA leader Adalberto Costa Junior, 60, repeated that the former rebel movement does "not recognise the final results" from the national electoral commission.
"We will do everything to ensure that all votes are effectively counted and respected," he said.
The MPLA has traditionally wielded control over the electoral process and opposition and civic groups had raised fears of vote tampering.
Four of the 16 electoral commissioners did not sign off on the final results, expressing doubts about the process.
The complaint with the electoral commission is the first step in a process that can take more than a week.
Earlier on Thursday, Artur Torres, a spokesman for the country's Constitutional Court, explained that after the commission reaches a decision, the complainant can appeal before the court.
In his video address, Costa Junior said he expected that the commission and the constitutional court would "truly perform their functions".
"We have been at peace for twenty years and we need to embrace a truly democratic and lawful state," he said.
The MPLA has been the only party to govern Angola since it gained independence from Portugal in 1975.
But the ruling party saw its poorest showing this year, down from its victory with 61 percent of the vote in 2017.
Turnout was low, with only about 45 percent of those registered casting their ballots.
Angola held a funeral last Sunday for long-serving former president Jose Eduardo dos Santos who was at the head of the MPLA from 1979 until 2017.