BUJUMBURA, Burundi - Burundi goes to the polls Tuesday with President Pierre Nkurunziza 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 his candidacy as unconstitutional and a violation of the 2006 peace deal that ended a dozen years of civil war and ethnic massacres in 2006.
Hours before the polls were due to open, explosions and gunfire rang out late Monday in the capital Bujumbura, the epicentre of three months of anti-government protests.
AFP journalists heard at least three explosions and sustained bursts of gunfire shortly before 11:00 pm (2000 GMT).
Residents in the suburb of Ngagara to the north of the city, Nyakabiga in the northeast and Kanyosha in the south all reported hearing blasts and gunshots, with police and unknown assailants trading fire in at least one area. No information on casualties was immediately available.
Earlier Monday, a grenade was lobbed from a passing car into a street close to the symbolic Independence Square in central Bujumbura. There were no reports of injuries.
Willy Nyamitwe, Nkurunziza's chief communications advisor, condemned the attacks as "terrorist acts" aimed at "intimidating voters".
Critics fear a win by the incumbent will be a hollow victory, leaving him ruling over a deeply divided nation.
"Despite a facade of pluralism, this is an election with only one candidate, where Burundians already know the outcome," said Thierry Vircoulon from the International Crisis Group, a think-tank that has warned the situation has all the ingredients to kick-start renewed civil war.
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.
Around 3.8 million Burundians are eligible to vote between 06:00 (0400 GMT) and 16:00 (1300 GMT).
Months of violence
More than two months of anti-Nkurunziza protests, which were violently repressed, have left 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.
Doctors Without Borders (MSF) said Monday around a thousand people were fleeing each day into Tanzania, crossing the border "through the forest ... many travelling in the dark on foot and without belongings." In mid-May, rebel generals attempted to overthrow Nkurunziza in a coup. After that failed they launched a rebellion in the north of the country.
Last-ditch crisis talks mediated by Uganda broke down on Sunday.
"The government has opted to isolate itself and go ahead with pseudo-elections," said Leonce Ngendakumana, a prominent opposition figure, after talks collapsed.
"They have refused to save Burundi from sliding into an abyss," said another opposition figure, Jean Minani.
A poor and landlocked former Belgian colony, Burundi is situated in the heart of central Africa's troubled Great Lakes region.
Analysts say renewed conflict in the country could reignite ethnic Hutu-Tutsi violence and bring another humanitarian disaster on the region.
The conflict also risks drawing in neighbouring states - much like in the war-torn east of the Democratic Republic of Congo.
The last civil war in Burundi left at least 300,000 dead.
Nkurunziza's CNDD-FDD party scored a widely-expected landslide win in parliamentary polls held on May 29 that were boycotted by the opposition and condemned internationally as neither free nor fair.
The results of parliamentary polls took a week to be announced.
The presidential elections are likely to be seen in the same light, diplomats said, meaning Nkurunziza - whose nation is heavily aid-dependent - will probably also face international isolation.