Sri Lankans are going to the polls in a general election, with former President Mahinda Rajapaksa aiming to return to office as prime minister.
Mr Rajapaksa lost the presidency in a snap election in January to Health Minister Maithripala Sirisena.
Four people have died in violent incidents during the campaign although monitors say there has been less violence than in previous years.
Fifteen million people are eligible to vote, with results expected on Tuesday.
Polls opened at 07:00 local time (01:30 GMT) and will close at 16:00.
Mr Rajapaksa is seeking to return as prime minister of a government led by the Sri Lanka Freedom Party. President Sirisena, who now leads the party, has threatened to veto the move.
The former president, who is 69, is thought of as a hero by many of Sri Lanka’s Sinhala-speaking Buddhist majority for crushing a 26-year Tamil uprising in 2009.
But opponents accuse him of running a corrupt, brutal and dynastic regime – charges he denies.
Ethnic tensions between the majority Sinhalese and the Tamil minority were the driving force behind a long and bitter civil war in the country.
The conflict ended in May 2009 after more than 25 years of violence but recriminations over abuses by both sides continue.
Mr Sirisena, 63, formed a cross-party coalition to defeat Mr Rajapaksa in January, led by the United National Party (UNP).
Having left his position as health minister in Mr Rajapaksa’s government, he led the coalition to a shock victory over the incumbent president.
In a letter leaked during the campaign, Mr Sirisena accused Mr Rajapaksa of holding the party “hostage” and ruled out naming him prime minister.
The current president has also used his power as party leader to purge Rajapaksa loyalists from key posts in recent days.
“We all united and voted against Rajapaksa to send him into retirement,” Prime Minister Ranil Wickremesinghe said at his last campaign stop on Friday night.
“If he hasn’t got the message, we should unite to make sure he understands it now.”