Left-leaning Anura Dissanayake claims victory in Sri Lanka's ...

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 statement at the Election Commission after the results were declared, Mr Dissanayake said he wanted to unite Sri Lankans.

"There are people who didn't vote for me," he said.

"I will take the country forward for all of them."

Sri Lankan president elect Anura Dissanayake won just 3 per cent of the vote at the 2019 election. (ABC News: Ellie Grounds)

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

Mr Dissanayake polled 42.3 per cent of the vote, or 5.63 million ballots, in the first round. His total vote count after preferences was 5.74 million.

Mr Premadasa was second at 32.8 per cent after the first round of counting of ballots on Sunday, or at 4.36 million. His total vote count after preferences was 4.53 million.

Mr Wickremesinghe received 17.3 per cent of the vote, or 2.29 million votes.

Members of National People's Power celebrate the election results outside the party office in Jaffna, Sri Lanka.   (Reutesr: Navesh Chitrakar)

The election result is largely seen as a rejection by Sri Lankans of the political establishment.

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.

During his campaign, he promised to root out corruption in Sri Lankan politics and renegotiate the country's bailout agreement with the International Monetary Fund.

The election was also an assessment on Mr Wickremesinghe's navigation of that agreement.

He 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.

Supporters of Anura Dissanayake brought a cake to his party's headquarters to celebrate his win.   (Reuters: Stringer)

In a statement, the outgoing president said he would entrust Mr Dissanayake with "the beloved child of Sri Lanka".

Mr Premadasa also pledged to support Mr Dissanayake's presidency.

Supporters of Mr Dissanayake gathered outside the Election Commission on Sunday night, while the result was announced, to celebrate, chanting "AKD" — his widely-used nickname — and setting off fireworks.

He is expected to be sworn in as president on Monday.