Recently declared results place the Movement for the Liberation of Angola as the winner with 51.17 percent of the vote, securing a second term for President Joao Lourenco.
Angola's leading opposition party says it has filed a legal complaint challenging recently announced election results, which saw the long-ruling MPLA win by a significantly reduced 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 news agency via WhatsApp on Thursday.
The August 24 elections were the most hotly contested in the oil-rich country since its first multi-party vote in 1992.
Results 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 earlier this week, the former rebel movement led by Adalberto Costa Junior, 60, said it did not "recognise the results" from the national electoral commission, alleging discrepancies in the count.
UNITA has filed challenges after previous elections, but without success.
The MPLA has been the only party to govern the country since it gained independence from Portugal in 1975, but saw its poorest showing in this year's ballot, down from its victory with 61 percent in 2017.