Sri Lanka's Parliament was preparing Tuesday to accept nominations to elect a successor to its ousted president, amid political turmoil that threatens to worsen instability as the country endures its most severe economic crisis in recent memory.

Gotabaya Rajapaksa fled the country last week after protesters outraged by the crisis stormed his official residence and occupied other key public buildings. He later submitted his resignation via an email to the speaker of the parliament.

Three lawmakers— the leader of the main opposition Sajith Premadasa, former government minister Dallas Alahapperuma and Marxist party leader Anura Dissanayake have said they will contest Wednesday's parliamentary vote.

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Acting President and Prime Minister Ranil Wickremesinghe has not said he will run, but statements from Rajapaksa's party, which still holds a majority in Parliament, expressed backing for him. This has angered many who see his possible election as an extension of the Rajapaksa rule and a potential comeback for the beleaguered political family.

Separately on Tuesday the Supreme Court was set to decide whether Wickremesinghe's appointment as acting president last week by the speaker of the parliament was legal. If it is pronounced illegal, Wickremesinghe may become ineligible to run for president.

Students and political activists said they planned protests Tuesday. Some intimidating posts circulating on social media warned lawmakers against returning to their constituencies if they vote for Wickremesinghe.

Parliament was heavily guarded by hundreds of soldiers, its entry points barricaded. Staff at parliament and reporters were thoroughly searched before they were allowed to enter.

Sri Lanka's economy has collapsed, its foreign exchange reserves depleted, and it has suspended repayment of foreign loans. Its population is struggling with shortages of essentials like medicine, fuel and food.

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The government is in talks with the International Monetary Fund for a bailout package and is preparing a loan restructuring plan as a prelude to that.

Rajapaksa's exit last week marked at least a temporary dismantling of the Rajapaksa dynasty that had ruled Sri Lanka for most part of the past two decades.

Before the recent upheavals, six family members held high positions including president, prime minister and finance minister. All have lost their positions after public protests started in late March.