Angolan President Jose Eduardo dos Santos casts his vote in the general election on Friday.
This is only the third time the nation has gone to the polls since independence from Portugal in 1975.
Long time leader dos Santos is widely tipped to win.
But many Angolans are unhappy about the unequal distribution of the country's oil wealth.
Presidential challenger, Abel Chivukuvuku, broke from former rebel group and main opposition party UNITA.
His new party is now expected to split the opposition vote.
Several of his colleagues were arrested on Thursday after they tried to enter the electoral commission building, demanding credentials to observe the vote at polling stations.
Chivukuvuku told media the accreditation process was done in a ''very messy and disorganised way.''