Bulgarians have gone to the polls to elect a president for a five-year term.
Incumbent Georgi Parvanov has a large lead in the Bulgarian presidential election, according to exit polls, but faces a run-off due to low turnout.
Incumbent Georgi Parvanov - who negotiated Bulgaria's entry into the EU - is expected to beat far-right candidate Volen Siderov.
Exit polls gave the Socialist leader more than 60% of the vote in the first round but turnout was said to have fallen below the 50% threshold.
Mr Parvanov is thought to be leading Mr Siderov by a large margin, but his supporters fear the election may still have to go to a second ballot.
If confirmed, he would face a run-off next Sunday against nearest rival, ultra-nationalist leader Volen Siderov.
Only 20% of eligible voters had turned out halfway through the day, fuelling fears of an inconclusive result.
Exit polls gave Mr Siderov just over 20% of the vote.
Voter 'apathy'
Mr Parvanov's first reaction was to thank supporters for the "convincing result".
The winning candidate needs to have at least 50% of the vote or else the election goes into a second round next Sunday.
He said of the run-off: "When one has such a ratio, there is nothing to worry about."
Polling stations in the Balkans state are due to close at 1600GMT.
Nato membership
We should all vote and make a good choice Voter Stoyan Minchev
An exit poll by the National Centre for Public Opinion Surveys put the turnout at just 38%.
Voter apathy is thought to be largely responsible for the electorate turning out in such low numbers.
A second, by Gallup, put the figure at 39.97% an hour before polling closed.
Stoyan Minchev, a 69-year old pensioner voting at a polling station at Sofia's Zapaden Park, said he wanted "a president with indisputable integrity and moral authority", the AP news agency said.
It gave Mr Parvanov 64.6% to 20.3% for Mr Siderov of the Attack party.
"They say the president has no powers so why vote, but he is our head of state after all, we should all vote and make a good choice," the agency quoted him as saying.
BBC Central Europe reporter, Nick Thorpe, says President Parvanov will be both satisfied and frustrated by the result.
Mr Siderov, a flamboyant former TV host, has verbally attacked Bulgaria's Turkish and Roma minorities in the run-up to the election.
Our correspondent says Mr Parvanov looks set to win next Sunday although the deep poverty of a significant part of the population and disagreements over Nato membership have helped Mr Siderov and his nationalists.
The BBC's Oana Lungescu says he has also capitalised on public anger with conventional politicians for their perceived failure to tackle poverty, corruption and organised crime.
Next Sunday the candidate who secures most votes will win, regardless of turnout.
Despite strong economic growth, Bulgaria will become the EU's poorest country once it joins, with half of its eight million people living under the poverty threshold.
The president is largely a figurehead position as power lies with the prime minister.
The third main candidate, running for a group of centre-right parties, is a former judge in his 70s, Nedelcho Beronov.
Low turnout expected
Mr Parvanov, who is backed by the ruling socialist party, is credited with forming the centre-left coalition that has spearheaded Bulgaria's efforts to join the EU.
A former historian, he has reshaped the hard-line communist party into the pro-Western socialists, ensured that Bulgaria joined Nato in 2004, and is on track to become a member of the EU next January.
Our correspondent says he remains one of Bulgaria's most popular politicians, but is facing a stronger challenge than expected from Mr Siderov, who has been compared to the French ultra-nationalist Jean-Marie Le Pen.
The role of the Bulgarian president is largely ceremonial, although he heads the army and can veto any bill.
Mr Parvanov is facing six challengers, but only Mr Siderov is considered a realistic rival.
