Hundreds of opposition supporters gathered in the Angolan capital Luanda on Saturday to protest against changes to the electoral law that they say will undermine the transparency of next year's general election.
President Joao Lourenço introduced a bill this week to centralise the counting of votes instead of doing it at the level of each municipality and province.
All opposition MPs abstained or voted against the reform, but they had little influence in a parliament largely dominated by the ruling Popular Movement for the Liberation of Angola (MPLA).
The main opposition party, Unita (National Union for the Total Independence of Angola), organised a march on Saturday, supported by other political movements and civil society groups, to demand "free and fair elections".
Unita proposed a series of measures to prevent alleged fraud, including biometric identification of voters and the involvement of civil society in the counting of ballots.
Hundreds of demonstrators gathered in the capital, waving Unita and Angolan flags while chanting "MPLA get out" in Portuguese.
They marched through the city centre holding placards that read: "Demand our rights" and "We want biometric control". Police armed with batons surrounded the demonstration.
Meanwhile, Lourenço has also sparked controversy for wanting to change another electoral law, which he recently submitted to the National Assembly with suggested amendments.
Elected in 2017 after his predecessor, Jose Eduardo dos Santos, stepped down after a 38-year reign, Joao Lourenço is expected to seek a second term in the 2022 presidential, parliamentary and local elections.
The MPLA has ruled the African country since its independence from Portugal in 1975.