Prime Minister Ranil Wickremesinghe has been sworn in as Sri Lanka’s interim president until Parliament elects a successor to Gotabaya Rajapaksa, who resigned after mass protests over the country’s economic collapse forced him from office.

The speaker of Sri Lanka’s Parliament said lawmakers will convene on Saturday to choose a new leader after Mr Rajapaksa resigned.

Their choice would serve out the remainder of Mr Rajapaksa’s term ending in 2024, said Speaker Mahinda Yapa Abeywardana.

He promised a swift and transparent process that should be done within a week.

The new president could appoint a new prime minister, who would then have to be approved by Parliament. With Mr Rajapaksa out, pressure on Mr Wickremesinghe was rising.

In a televised statement, Mr Wickremesinghe said he would initiate steps to change the constitution to curb presidential powers and strengthen Parliament, restore law and order and take legal action against “insurgents”.

Referring to clashes near Parliament on Wednesday night when many soldiers were reportedly injured, Mr Wickremesinghe said true protesters will not get involved in such actions.

“There is a big difference between protesters and insurgents. We will take legal action against insurgents,” he said.

Mr Wickremesinghe became the acting president afterMr Rajapaksa fled Sri Lanka on Wednesday, flying first to the Maldives and then to Singapore.

The prime minister’s office said Mr Wickremesinghe was sworn in on Friday as interim president before Chief Justice Jayantha Jayasuriya.

Sri Lanka has run short of money to pay for imports of basic necessities such as food, fertiliser, medicine and fuel, to the despair of its 22 million people.

Its rapid economic decline has been all the more shocking because, before this crisis, the economy had been expanding, with a growing, comfortable middle class.

Protest leader Jeewantha Peiris, a Catholic priest, said they are “happy because we have come through a hard journey”.

“We are happy, as a collective effort because this struggle of Sri Lanka was participated by all the citizens of Sri Lanka, even diaspora of Sri Lanka,” he said.

Protesters cooked and distributed milk rice — a food Sri Lankans enjoy to celebrate victories — after Mr Rajapaksa’s resignation. At the main protest site in front of the president’s office in Colombo, people welcomed his resignation but insisted Mr Wickremesinghe also should step aside.

“I am happy that Gotabaya has finally left. He should have resigned earlier, without causing much problems,” Velayuthan Pillai, 73, a retired bank employee, said as patriotic songs were blaring from loudspeakers.

But he added that “Ranil is a supporter of Gotabaya and other Rajapaksas. He was helping them. He also must go.”

The capital regained a tenuous calm after protesters who had occupied government buildings retreated on Thursday. But with the political opposition in Parliament fractured, a solution to Sri Lanka’s many woes seemed no closer.

The military warned on Thursday that it had powers to respond in case of chaos — a message some found ominous.

Mr Abeywardana, the speaker of Parliament, urged the public to “create a peaceful atmosphere in order to implement the proper parliamentary democratic process and enable all members of Parliament to participate in the meetings and function freely and conscientiously.”

Sri Lanka is seeking help from the International Monetary Fund and other creditors, but its finances are so poor that even obtaining a bailout has proven difficult, Mr Wickremesinghe said recently.