Troops armed with sweeping powers to detain suspects were deployed in Sri Lanka Saturday, hours after the president declared a state of emergency as protests against him escalated.

Gotabaya Rajapaksa invoked the emergency on Friday night, a day after hundreds tried to storm his house in anger over unprecedented shortages of food, fuel and medicine.

The emergency was for the "protection of public order and the maintenance of supplies and services essential to the life of the community", Rajapaksa said in a proclamation.

Soldiers armed with automatic assault rifles were already deployed for crowd control at fuel stations and elsewhere when the emergency was invoked. More were seen on Saturday.

"Before the emergency, the military could not act on its own and had to play a supportive role to the police, but since Friday they are on their own and they have more powers," a police official said.

The emergency laws came ahead of planned anti-government protests on Sunday, when activists on social media have been urging people to demonstrate outside their homes.

The South Asian nation of 22 million is facing severe shortages of essentials, sharp price rises and crippling power cuts in its most painful downturn since independence from Britain in 1948.

The coronavirus pandemic torpedoed tourism and remittances, both vital to the economy, and authorities imposed a broad import ban in an attempt to save foreign currency.

Many economists also say the crisis has been exacerbated by government mismanagement, years of accumulated borrowing, and ill-advised tax cuts.

A curfew reimposed for a second night Friday was relaxed at dawn Saturday.

Thursday night's unrest outside the president's private home saw hundreds of people demand he step down. 

People chanted "lunatic, lunatic, go home", before police fired tear gas and used water cannon.

The crowd turned violent, setting ablaze two military buses, a police jeep and other vehicles, and threw bricks at officers.

Police arrested 53 protesters and 21 of them were released on bail on Friday night, court officials said. Others were still being detained but had yet to be charged.

Rajapaksa's office said Friday that the protesters wanted to create an "Arab Spring" -- a reference to anti-government protests in response to corruption and economic stagnation that gripped the Middle East more than a decade ago.