Sri Lankan authorities deployed armoured vehicles and troops on the streets of the capital on Wednesday, a day after pro-government mobs attacked peaceful protesters, triggering a wave of violence across the country.

Security forces have been ordered to shoot those deemed to be participating in the violence, as sporadic acts of arson and vandalism continued into a second day despite a strict curfew that began on Monday evening.

Armoured trucks with soldiers riding atop were seen rolling into some areas of Colombo, where the government is facing its severest challenge in decades as the country plunges into economic crisis and protests.

Videos posted on social media showed lines of military trucks moving out of the capital and soldiers setting up checkpoints across the country, amid fears that a political vacuum could pave the way for a military takeover.

Nationwide protests have been calling for the resignations of President Gotabaya Rajapaksa and his brother, who stepped down as prime minister this week, over a debt crisis that has nearly bankrupted Sri Lanka and left its people facing shortages of fuel, food and other essentials.

After Mahinda Rajapaksa resigned, he and his family were evacuated from his official residence through thousands of protesters trying to break into the heavily guarded, colonial-era building. There was no confirmation on their whereabouts, but some protesters gathered outside a well-fortified naval base in Trincomalee on the northeastern coast claiming the Rajapaksa family was being protected there.

The Indian Embassy denied social media speculation that “certain political persons and their families have fled to India," and also rejected speculation that India was sending troops into Sri Lanka.

The country reaffirmed its support to Sri Lanka on Tuesday, saying India had extended support of US$3.5 billion to help it overcome the crisis, as well sent essential items like food and medicine, the Ministry of External Affairs in New Delhi said.

President Gotabaya Rajapaksa remained in his official residence protected by layers of iron barriers guarded by the military and police. (AP)