Leftist alliance leader Anura Kumara Dissanayake will be Sri Lanka's new president, after he won an historic election that came two years after the peak of the country's unprecedented economic crisis.

For the first time in the country's history, a second round of vote counting looking at preferences was needed to determine the winner, because no candidate won the required 50 per cent in the first round.

The second round was a run-off between Mr Dissanayake and opposition leader Sajith Premadasa.

Incumbent President Ranil Wickremesinghe trailed in third.

In a post on X, Mr Dissanayake said, "This victory belongs to all of us. Together, we stand ready to rewrite Sri Lankan history."

Mr Dissanayake, who does not possess political lineage like some of his rivals in the presidential election, led from start to finish during the counting of ballots.

The election was also a referendum on Mr Wickremesinghe, who led the heavily indebted nation's fragile economic recovery from a meltdown in 2022 but the austerity measures that were key to this recovery hindered his bid to return to office.

He finished third with 17 per cent of the vote.

Mr Dissanayake polled 5.6 million or 42.3 per cent of the votes, a massive boost to the 3 per cent he managed in the last presidential election in 2019.

Mr Premadasa was second at 32.8 per cent after the first round of counting of ballots on Sunday.

ABC/Reuters