Sri Lanka's anti-government demonstrators said Thursday they were ending their occupation of official buildings, as they vowed to press on with their bid to bring down the president and prime minister in the face of a dire economic crisis.

Protesters overran President Gotabaya Rajapaksa's palace at the weekend, forcing him to flee to the Maldives on Wednesday, when activists also stormed the office of Prime Minister Ranil Wickremesinghe.

Rajapaksa, 73, flew onwards Thursday to Singapore from Male, but there was still no announcement of his resignation, despite his earlier promise to step down on Wednesday.

He is expected to look to stay in the city-state for some time, according to Sri Lankan security sources, before potentially moving to the United Arab Emirates. 

As president, Rajapaksa enjoys immunity from arrest, and he is believed to have wanted to go abroad before stepping down to avoid the possibility of being detained. 

Hundreds of thousands of people have visited his compound since it was opened to the public after he fled and his security guards backed down.

At the site, business owner Gihan Martyn, 49, accused him of "playing for time".

"He's a coward," he said. "He ruined our country along with the Rajapaksa family. So we don't trust him at all. We need a new government."

Security sources in Colombo said Rajapaksa's resignation letter had already been prepared. 

"No sooner he gives the green light, the Speaker will issue it," a source told AFP.

But Wickremesinghe, whom Rajapaksa named as acting president in his absence, demanded the evacuation of occupied state buildings and instructed security forces to do "what is necessary to restore order", as a nationwide state of emergency and curfew were declared.

A spokeswoman for the protesters announced Thursday: "We are peacefully withdrawing from the Presidential Palace, the Presidential Secretariat and the Prime Minister's Office with immediate effect, but will continue our struggle."

A top Buddhist monk who has supported the protests had earlier called for the more than 200-years-old presidential palace to be handed back to authorities and ensure its valuable art and artefacts were preserved.

"This building is a national treasure and it should be protected," monk Omalpe Sobitha told reporters. "There must be a proper audit and the property given back to the state."

The curfew was lifted at dawn on Thursday before being reimposed in the capital later in the day.

Police said a soldier and a constable were injured in overnight clashes with protesters outside the national parliament.

The attempt on the legislature was beaten back, unlike at other locations where the protesters had spectacular success. 

The main hospital in Colombo said about 85 people were admitted with injuries on Wednesday, with one man suffocating to death after being tear-gassed at the premier's office.

But student Chirath Chathuranga Jayalath, 26, said: "You cannot stop this protest by killing people. They'll shoot our heads but we do this from our hearts."

- Jeers -

According to Maldivian media, Rajapaksa was jeered and insults thrown at him at Male airport on Wednesday, while another group staged a demonstration in the capital urging authorities not to allow him safe passage.

Maldivian media reported that he had spent the night at the Waldorf Astoria Ithaafushi super luxury resort.

They contrasted the opulent accommodation with the economic plight of his compatriots -- four out of five Sri Lankans skipping meals because of the country's dire economic crisis.

Rajapaksa is accused of mismanaging the economy to a point where the country has run out of foreign exchange to finance even the most essential imports, leading to severe hardships for its 22 million people.

Sri Lanka defaulted on its $51-billion foreign debt in April and is in talks with the IMF for a possible bailout.

The island has nearly exhausted its already scarce supplies of petrol with the government ordering the closure of non-essential offices and schools to reduce commuting and save fuel.

Diplomatic sources said Rajapaksa's attempts to secure a visa to the United States had been turned down because he had renounced his US citizenship in 2019 before running for president.