Bujumbura -Vote counting was under way in Burundi on Wednesday, the day after a presidential election marred by violence and international condemnation that is expected to see incumbent Pierre Nkurunziza win a controversial third term.Results from the polls, which has been condemned as illegitimate by the international community after sparking months of deadly violence that forced tens of thousands to flee the country, are expected by the end of Thursday.Electoral Commission president Pierre-Claver Ndayicariye said around 74% of the country's 3.8 million registered voters cast their ballot, comparable to last month's general elections, despite a boycott from opposition lawmakers.At least two people - a policeman and a civilian - were killed overnight before the polls opened on Tuesday in what Nkurunziza's chief communications advisor called "terrorist acts" aimed at "intimidating voters".Ndayicariye said turnout was depressed in southwestern Bururi province and Bujumbura, the epicentre of three months of anti-government protests where gunfire and grenade blasts could be heard as polls opened.The 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".The US on Tuesday said the government's refusal to delay the vote threatened its legitimacy and risked "unravelling the fragile progress" made by the peace deal that ended more than a decade of civil war and ethnic massacres in 2006.Opposition and civil society groups have denounced Nkurunziza's candidacy as unconstitutional, while international observers have said the elections are not free and fair. An AFP journalist observed irregularities at polling stations in the capital, including blank tally sheets being signed before counting began. State radio said an election official was arrested after being caught red-handed stuffing a ballot box at a polling station outside the capital.'Facade of pluralism' The 51-year-old president - a former rebel, born-again Christian and soccer fanatic - is facing no serious competition, but critics say a win by the incumbent will be a hollow victory, leaving him ruling over a deeply divided nation.Although eight candidates are on the ballot paper, most have already withdrawn from the race and those remaining are not seen as having a chance as the unrest and the closure of most independent media have stopped them campaigning.Key opposition leader Agathon Rwasa did not formally withdraw, but said the election could not be free or fair and did not attempt to win votes. In one polling station in the capital, voters were seen scrubbing off indelible ink from their fingers to avoid reprisals from opposition supporters boycotting the ballot.The International Crisis Group think-tank has warned that the situation has all the ingredients to plunge Burundi into civil war."Despite a facade of pluralism, this is an election with only one candidate, where Burundians already know the outcome," said the ICG's Thierry Vircoulon.Former colonial ruler and key aid donor Belgium said the polls "do not meet the minimal requirements of inclusiveness and transparency", and repeated warnings it would "review its cooperation" with Bujumbura.Anti-Nkurunziza protests have been violently repressed, leaving at least 100 people dead since late April. Many opponents have also fled - joining an exodus of more than 150 000 ordinary Burundians who fear their country may again be engulfed by widespread violence.Nearly 10 000 Burundians fled the country over the last weekend of June before Burundi closed its borders ahead of the election, according to the UN.Doctors Without Borders (MSF) said on Monday around 1 000 people were fleeing each day into Tanzania, crossing the border "through the forest... many travelling in the dark on foot and without belongings".'Sliding into an abyss'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.Crisis talks mediated by Uganda broke down on Sunday, after several previous UN-backed rounds collapsed, failing to resolve the central African nation's political crisis."They have refused to save Burundi from sliding into an abyss," said opposition leader Jean Minani, who like almost all others boycotted Tuesday's poll.Poor and landlocked, Burundi is 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 last civil war in Burundi left at least 300 000 people dead.Nkurunziza's CNDD-FDD party scored a widely expected landslide win in last month's parliamentary polls that were boycotted by the opposition.The UN electoral observers - some of the few international monitors in Tuesday's poll - said the last round of voting took place in a "climate of widespread fear and intimidation".The presidential election is likely to be seen in the same light, diplomats said, meaning Nkurunziza - whose nation is heavily aid-dependent - will probably also face international isolation.