Burundians go to the polls today to vote for the president amid sporadic violence in parts of the capital Bujumbura.
Gunfire and grenade blasts have been heard as President Pierre Nkurunziza seeks a third controversial term.
Mr Nkurunziza is widely expected to win a third consecutive term despite international condemnation and thousands of people fleeing feared violence.
Opposition and civil society groups have denounced Nkurunziza’s candidacy as unconstitutional and a violation of a peace deal that ended a dozen years of civil war and ethnic massacres in 2006.
Around 3.8 million Burundians are eligible to vote.
UN Secretary General Ban Ki-moon urged calm, calling on all sides to “refrain from any acts of violence that could compromise the stability of Burundi and the region.”
Critics fear a win by the incumbent will be a hollow victory, leaving him ruling over a deeply divided nation.
With the elections denounced by the opposition as a sham, the 51-year-old president — a former rebel, born-again Christian and football fanatic — is facing no serious competition.
Anti-Nkurunziza protests have been violently repressed, leaving at least 100 dead since late April.
Independent media has been shut down and many opponents have fled — joining an exodus of over 150,000 ordinary Burundians who fear their country may again be engulfed by widespread violence.