Sri Lanka's acting President Ranil Wickremesinghe, main Opposition leader Sajith Premadasa are among the four leaders who have joined the race to become the country's next President as the lawmakers met on Saturday to start the process of electing a new president to succeed Gotabaya Rajapaksa, who resigned after unprecedented protests against his government over the country's economic collapse.

Besides Wickremesinghe and Premadasa, Marxist JVP leader Anura Kumara Dissanayake and Dullas Alahapperuma, a breakaway SLPP candidate, are the other two leaders who have so far announced their candidacy to contest the July 20 vote in Parliament to succeed Rajapaksa for the rest of his term until November 2024 after he resigned on Thursday.

Parliament met for a brief special session on Saturday to announce the vacancy in the presidency following the resignation of Rajapaksa.

Rajapaksa, who fled to the Maldives on Wednesday and then landed in Singapore on Thursday, formally resigned on Friday, capping off a chaotic 72 hours in the crisis-hit nation that saw protesters storm many iconic buildings, including the President and the Prime Minister's residences here.

During the 13-minute special session, Dhammika Dassanayake, Secretary General of Parliament, announced the vacancy for the post of president.

Dasanayake said that nominations for the election of the new president will be heard on Tuesday and if there is more than one candidate, the lawmakers will vote on Wednesday.

Marxist Janatha Vimukthi Peramuna (JVP) leader Dissanayake, 53, on Saturday officially declared his intention to contest the election.

The main reason for this is that we feel that our party and our leader represents many of the aspirations and in fact the spirit of the people's movement that has been taking place in our country for so long," his party's spokesperson Harini Amarasuriya told reporters.

Main Opposition Samagi Jana Balawegaya (SJB) leader Premadasa, while officially declaring his intention to contest the vote, said, "Even though it is an uphill struggle, I am convinced that truth will prevail."

The 225-member Parliament is dominated by Rajapaksa's ruling Sri Lanka Podujana Peramuna (SLPP) party.

The ruling SLPP which officially announced its backing for Wickremesinghe, the acting president, found some resistance to its decision from within.

Its chair GL Peiris said the party should not vote for anyone other than its own member. He said the party must back Alahapperuma, a breakaway SLPP candidate who has put himself forward to the vote.

The party is to meet on Saturday to make the final decision. For the first time since 1978, Sri Lanka will elect the crisis-hit country's next president through a secret vote by the MPs and not through a popular mandate, following the resignation of Rajapaksa.

Never in the history of the presidency since 1978, Parliament had voted to elect a president.

Presidential elections in 1982, 1988, 1994, 1999, 2005, 2010, 2015 and 2019 had elected them by popular vote.

The only previous occasion when the presidency became vacant mid-term was in 1993 when president Ranasinghe Premadasa was assassinated. DB Wijetunga was unanimously endorsed by Parliament to run the balance of Premadasa's term.

The front runner in next week's race would be Wickremesinghe. The 73-year-old became prime minister from nowhere in May when he assumed the job to handle the unprecedented economic crisis.

His United National Party (UNP) was routed in the 2020 parliamentary election. Wickremesinghe for the first time failed to win a seat since 1977. He made it to Parliament in late 2021 through the party's only seat allocated on the basis of a cumulative national vote.

Without parliamentary numbers of his own, Wickremesinghe would be entirely dependent on the ruling SLPP member vote.

Premadasa, 55, for long the understudy of Wickremesinghe was the one who turned the tables on his former leader. His newly formed SJB ousted the grand old party of Wickremesinghe from all its bastions to emerge as the main opposition in 2020.

Ironically, it was his failure to step in to fill the power vacuum in mid-May which made way for Wickremesinghe to become Prime Minister from nowhere.

He only stands an outside chance as most ruling SLPP members are unlikely to back him. Alahapperuma, 63, is from the breakaway group of the ruling SLPP.

The ex-Cabinet Minister of Information and Mass Media and former newspaper columnist is being seen as left-leaning political ideologue. Held ministerial positions since 2005 and enjoys the reputation of having a clean public life. His task too would be uphill given his position as a breakaway member.