Voters are heading to the polls Thursday in Sri Lanka's presidential election.

Some 15 million people are eligible to cast ballots across the country.

President Mahinda Rajapaksa is seeking a third term. He won 58 percent of the vote in the last election, surfing a wave of popularity after 2009 defeat of Tamil Tiger separatists who had waged a 26-year war against the government.

He's facing an unexpected challenge from his former health minister Mithripala Sirisena, who crossed to the other side to become the opposition's candidate in November, triggering a flood of defections from the government.

While there have been no reliable opinion polls ahead of the vote, many believe Sirisena will benefit from a popular yearning for change after a decade under Rajapaksa.