Washington/Colombo: The US State Department said in a revised travel advisory 'terrorist groups' were continuing to plot possible attacks in Sri Lanka after 290 people were killed and about 500 wounded in blasts in churches and luxury hotels on Sunday.
"Terrorists may attack with little or no warning," it said in the revised warning, which was dated Sunday US time.
It said possible targets included tourist locations, transportation hubs, shopping malls, hotels, places of worship, airports and other public areas.
Lanka lifts curfew
Meanwhile, Lankan authorities lifted a curfew on Monday, although there was uncharacteristically thin traffic in the normally bustling capital.
There was still no claim of responsibility for the attacks on two churches and four hotels in and around Colombo, the capital of predominantly Buddhist Sri Lanka, and a third church on the country's northeast coast.
A government source said President Maithripala Sirisena, who was abroad when the attacks happened, had called a meeting of the National Security Council early on Monday. Prime Minister Ranil Wickremesinghe would attend the meeting, the source said.
There were fears the attacks could spark a renewal of communal violence, with police reporting late on Sunday there had been a petrol bomb attack on a mosque in the northwest and arson attacks on two shops owned by Muslims in the west.
The South Asian nation of about 22 million people has Christian, Muslim and Hindu populations of between about eight and 12 per cent.
Soldiers armed with automatic weapons stood guard outside major hotels and the World Trade Centre in the business district, where the four hotels were targeted on Easter Sunday, according to a Reuters witness.
Scores of people who were stranded overnight at the main airport began making their way home as restrictions were lifted.
The government also blocked access to social media and messaging sites, including Facebook and WhatsApp, making information hard to come by.
Wickremsinghe acknowledged on Sunday that the government had some prior information about possible attacks on churches involving a little-known Islamist group, but said ministers had not been told.