COLOMBO: Crisis-hit Sri Lanka lifted a curfew Saturday already defied by thousands of people overnight, ahead of a mass rally planned for later in the day demanding President Gotabaya Rajapaksa's resignation.

Huge crowds have already poured into the capital Colombo for the demonstration, the latest expression of unrest sparked by the country's unprecedented economic crisis.

Police withdrew the stay-home order issued the previous evening after opposition parties, rights activists and the bar association threatened to sue the police chief.

Thousands of anti-government protesters ignored the curfew and even forced railway authorities to operate trains to take them to Colombo for Saturday's rally, officials said.

"The curfew was not a deterrent, in fact it encouraged more people to get on the streets in defiance," a top defence official told AFP.

"Passengers had commandeered trains to reach Colombo."

Sri Lanka has suffered through months of food and fuel shortages, lengthy blackouts and galloping inflation after running out of foreign currency to import vital goods.

The country has nearly exhausted already scarce supplies of petrol, but protesters backed by main opposition parties, had hired private buses to travel to the capital.

Sri Lanka police impose curfew, fire tear gas as unrest escalates

Demonstrators have camped outside Rajapaksa's seafront office to demand his resignation over the government's mismanagement of the crisis.

Thousands of soldiers armed with assault rifles were bussed into Colombo on Friday to reinforce police guarding Rajapaksa's official residence, which protesters have vowed to storm on Saturday.

Authorities have deployed nearly 20,000 troops and police officers for a security operation to protect the president.

On Friday, three judges refused police requests to outlaw Saturday's protests.

The United Nations urged both authorities and protesters to ensure that Saturday's demonstrations were peaceful.

"We urge Sri Lankan authorities to show restraint in the policing of assemblies and ensure every necessary effort to prevent violence," the Office of the UN High Commissioner for Human Rights said.

Nine people were killed and hundreds wounded when clashes erupted across the country after Rajapaksa loyalists attacked peaceful protesters outside the president's office in May.

Sri Lanka has defaulted on its $51 billion external debt and has been in bailout talks with the International Monetary Fund.