President Pierre Nkurunziza, whose government has repeatedly been accused of rights abuses, will step down after 15 years. His ruling CNDD-FDD party candidate, retired army general Evariste Ndayishimiye, is running against opposition leader Agathon Rwasa and five others.

The government expelled the national head of the World Health Organization last week following public criticism that all parties were holding rallies despite the disease.

“We call on Burundians to vote in massive numbers and vote peacefully. We need good elections,” Pierre Claver Kazihise, chairman for the election commission said in comments aired by state broadcaster RTNB.

In the commercial city of Bujumbura, a Reuters witness said lines were long in the morning in Musaga neighbourhood, where the opposition is popular.

“The voting is really taking place smoothly and I voted for change but I am pessimistic about the counting of votes,” said one resident who did not wish to be named.

Several voters were worried that Twitter and WhatsApp – messaging services that can spread information quickly – seemed to be shut down.

The election is meant to usher in the first democratic transition in 58 years of independence for the impoverished east African nation, after widespread international criticism of its last election in 2015, when Nkurunziza won a third term.

His opponents said his participation violated a peace deal that ended the civil war and boycotted the poll.

That election sparked violent protests that drove hundreds of thousands of Burundians into exile. The United Nations documented hundreds of killings and the torture and gang-rape of opposition activists. Donors withdrew funding.

The government denies accusations of rights violations.

Rwasa, like Nkurunziza a former rebel leader, warned about possible electoral fraud on Sunday.

“We know there is plan of election fraud, some are even intimidating people asking for their voter cards to vote for them,” he said.

The United Nations and the African Union said on Sunday they remained “concerned about reports of intimidation and violent clashes between supporters of opposing sides”.

There will be few international election monitors after the government said they would have to spend 14 days in quarantine to prevent the spread of the coronavirus.

Full results are expected within a week – if no one wins 50% in the first round then a run-off is held within a fortnight.

Burundi has reported 42 coronavirus cases and one death. But only 633 tests have been carried out, according to the Africa Centres for Disease Control and Prevention. (Reporting by Nairobi Newsroom Editing by Giles Elgood)