Sunday’s vote for a new president in the Democratic Republic of Congo has been hit been hit by a series of delays that have left people frustrated.
The failure of new electronic voting machines in some polling stations is one of the challenges.
Close to 40 million people are eligible to vote for a successor to President Joseph Kabila – in power since 2001.
The poll is expected to bring the country’s first peaceful transfer of power since independence in 1960.
The election should have taken place two years ago but was repeatedly postponed because of logistical problems, officials said.
The run-up to the poll has been hit by violence and controversy over the decision to exclude some 1.26 million from voting.
Voting began at 05:00 (04:00 GMT) and ends at 17:00, but people still in the queue at that time will be allowed to vote.
Things started slowly in the capital, Kinshasa, because of heavy rain, reports the BBC’s Louise Dewast.
There have been delays in a number of areas because of problems with the electronic voting machines, which are being used for the first time.
There was frustration in Limete, a district of Kinshasa, as the electoral register had not been delivered and people were unable to vote.
Those waiting then booed the head of the electoral commission (Ceni), Corneille Nangaa, who had come to the scene.
The current president took over from his assassinated father Laurent in 2001, but he is barred from running for another term under the constitution.
He was supposed to step down two years ago, but the election was postponed after the electoral commission said it needed more time to register voters.
The decision triggered violent clashes, as the opposition accused Mr Kabila of trying to cling on to power.
Then last week, the election was delayed again, for seven days, because of problems deploying voting materials to polling sites.
This all came after thousands of electronic voting machines – being used for the first time – were destroyed in a fire in Kinshasa.
Speaking at a polling station, the president tried to address concerns about the voting, saying: “It’s clear that the elections are free and fair.”