Both candidates in Romania's presidential election claimed victory yesterday night after most early exit polls showed leftist challenger Mircea Geoana with a slim lead over centre-right incumbent Traian Basescu in a tense runoff.
Polls closed at 1900 GMT and first results are expected today.
"Together, we won," Social Democrat leader Geoana told supporters. "This is a beautiful night for Romanian democracy."
But Mr Basescu, an abrasive campaigner against corruption, said defiantly that "correct surveys" showed he had triumphed.
"I won like in 2004. I assure you that at 7 o'clock (1700 GMT), the correct surveys showed that I defeated Mircea Geoana," the President told supporters at his campaign headquarters.
"Millions of Romanians showed they had a clear option towards the modernisation of Romania... towards the reforms of the political class."
"I can assure you that... you can trust what I'm telling you now: We won." "My voters need to stay calm and convinced that the counting of votes cannot be subject to fraud."
The rival claims raised the prospect of a disputed outcome that may create uncertainty on Romanian markets, since official results are only expected today, at the earliest.
Analysts said the vote was one of Romania's most important since the fall of communism 20 years ago, as the winner must steer long-delayed reforms that could decide whether the country of 22 million can resume its convergence with the richer West.
On the other hand two exit polls broadcast after voting ended put Mr Geoana ahead.
A survey by CURS agency for public television TVR gave the challenger 50.8 per cent of ballots cast, versus 49.2 per cent for Mr Basescu. The margin of error was given as one percentage point.
Another poll by agency INSOMAR gave Mr Geoana a wider lead of 51.6 per cent to 48.4 per cent over the incumbent president.
Mr Geoana told his supporters, "Together, we won. This is a beautiful night for Romanian democracy."
Mr Geoana, who has pledged to end a political deadlock and an economic crisis, attracted many voters frustrated by clashes in Parliament over Mr Basescu's drive to root out corrupt politicians. The winner must name a new prime minister to replace a Basescu-allied Cabinet toppled by opposition lawmakers in October, and quickly enact a 2010 budget to release IMF aid.
Some analysts worry that Mr Geoana, 51, a former foreign minister and ambassador to Washington, may go soft on reforms, notably International Monetary Fund demands to cut up to 150,000 public jobs as part of a stalled €20 billion aid deal.
Mr Geoana struck a chord with voters by blaming Mr Basescu for polarising politics with his confrontational style, which helped lead to the untimely fall of two governments during his term.
"I hope we will have wisdom to choose unity, stability and the hope of a new start," Mr Geoana said after casting his vote.
Mr Basescu, an outspoken 58-year-old former ship captain, backs the IMF's belt-tightening proposals, saying they are crucial for the European Union newcomer to claw back from an expected eight per cent economic contraction this year. He has said Mr Geoana's party would turn a blind eye to high-level corruption which has plagued Romanians since they overthrew one of the Soviet era's most repressive regimes and executed dictator Nicolae Ceausescu 20 years ago this month.
The country is ranked the EU's most-corrupt by Transparency International.