Vote counting has started in Sri Lanka's tightly fought presidential election, in which millions have voted, with monitors and officials reporting high turnout, despite some reports of intimidation.

About 15 million people were eligible to vote in Thursday's election, as incumbent President Mahinda Rajapaksa faced Maithripala Sirisena, a former health minister and political ally who defected from the ruling party to run against him.

Early indications suggested national turnout could be as high as the near 75 percent reported in 2010. The country's election commissioner declared that the voting was "free and fair".

There were no major reports of violence, although the Campaign for Free and Fair Elections (CaFFE), a private monitoring group, said a small number of voters had been prevented from casting their ballots. 

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Tamil leaders said two explosions in the northern Jaffna peninsula were an attempt to deter voters, but there were no casualties and voting continued.

"A high turnout usually favours the opposition," Keerthi Thennakoon, CaFFE's head said.

Al Jazeera's Charles Stratford, reporting from the capital Colombo, said there were long queues at polling stations, with many voters eager to see a change in leadership.

Voting proceeded with few hitches elsewhere, but in Colombo the chief election commissioner visited a state-run television station to demand it correct a report that a prominent opposition leader had defected to Rajapaksa's camp.

The election observer group have said that there had been "unparalleled misuse of state resources and media" by Rajapaksa's party and that police inaction had given free rein to election-related violence.

The Sri Lankan president said he was confident of a "resounding victory" and promised a peaceful post-election period as he cast his ballot.

Opposition candidate Sirisena said victory was in sight.

"There is support for us everywhere. From tomorrow, we will usher in a new political culture," Sirisena said after casting his vote in the eastern town of Polonnaruwa.

He quit as one of Rajapaksa's ministers in November, triggering a flood of defections from the government.

The defection turned Rajapaksa's bid for a third term into a referendum on the president, and the enormous power he wields over the island nation.

Tight race

With more than 25,000 domestic and about 70 foreign monitors observing the vote, the election commission said it was confident the poll would be free and fair.

There are no reliable opinion polls, but many analysts believe Sirisena will benefit from a popular yearning for change after a decade under Rajapaksa.

Scars of Sri Lanka

Sirisena's election campaign focused on reining in the president's expanding powers, and accused Rajapaksa of corruption, a charge the president denies.

The opposition candidate has pledged to abolish the executive presidency that gave Rajapaksa unprecedented power and hold a fresh parliamentary election within 100 days.

Rajapaksa appeared assured of victory on Thursday, despite his second term being dogged by accusations of corruption, including undermining the independence of the judiciary and lining the pockets of political cronies through lucrative contracts.

"We will have a resounding victory. That is very clear," he told reporters.

After his landslide election victory in 2010, Rajapaksa jailed his opponent and used his overwhelming parliamentary majority to scrap a constitutional two-term limit for the president and give himself the power to appoint judges, top bureaucrats, police officials and military chiefs.

He also orchestrated the impeachment of the country's chief justice and replaced her with a trusted adviser.

Rajapaksa's political power grew immensely after he crushed the Tamil Tiger rebels in 2009, ending the country's 25-year civil war.

More than 100,000 people are estimated to have been killed, including 40,000 mostly Tamil civilians in the closing months of the conflict.

Source: Al Jazeera and agencies