Hundreds of opposition supporters have held a march in the Angolan capital, Luanda, to protest against changes to electoral laws.
Under the new legislation, votes will be tallied centrally instead of being counted in the regions.
Critics say this will reduce transparency.
The demonstration was organised by the main opposition Unita party and joined by other groups.
Unita has suggested the introduction of measures to counter electoral fraud including biometric voter identification and the involvement of civil society in ballot counting.
President João Lourenço is expected to run for a second term in next year’s poll.