Polling stations in Burundi opened at 06:00 local time (04:00GMT) on Wednesday with around five million voters expected to participate in the general elections.
Voters will be electing their president, members of parliament and communal council members.
Seven candidates are seeking to replace long-serving President Pierre Nkurunzinza, with the main contenders being Agathon Rwasa of the opposition CNL party and Evariste Ndayishimiye from the ruling CNDD-FDD party.
Voters in the diaspora will not cast their ballot because of the coronavirus pandemic.
Polling stations will close at 16:00 local time with preliminary results expected to be out on 25 May.
The electoral commission announced that there will be 53 international observers who include personnel for the embassies of Tanzania, Egypt, China, Kenya, South Africa, Democratic Republic of Congo, Nigeria, Russia and Africa Union mission in Burundi.
The commission has banned the use of mobile phones and cameras by observers and poll agents inside polling stations.
BBC Africa