The U.S. Embassy in Colombo has advised people to avoid places of worship in Sri Lanka over the coming weekend, citing Sri Lankan reports that additional attacks may occur.
"Continue to remain vigilant and avoid large crowds," the embassy said Thursday on its official Twitter account.
The warning comes days after a devastating attack on Christian worshipers on Easter Sunday when suicide bombers killed more than 250 people. Officials had earlier set the death toll at more than 350 but revised the number on Thursday, saying some of the bodies may have been counted twice.
Sri Lanka's Defense Secretary Hemasriri Fernando quit Thursday in the wake of the bombings, heeding calls from Sri Lanka's president for his resignation.
President Maithripala Sirisena had called on Fernando as well as the police chief Pujith Jayasundara to step down after he promised in a televised address to take stern action against officials who did not share with him the intelligence alerts that came from India days prior to the bombing of churches and luxury hotels.
As the government faces an outpouring of public anger over the failure to heed the warnings, senior officials admit it has been a "major lapse."
Fernando said that there had been no failure on his own part, but he resigned to take responsibility for the failures of some institutions he headed, Reuters reported.
Reports say Indian intelligence agencies sent out several warnings to Sri Lanka, and that Indian security agencies had gathered details about Islamic militant group National Thowfeek Jamaath (NTJ), which is suspected of carrying out the attacks.
The government also faces scrutiny on whether bitter political wrangling between Sirisena and Prime Minister Ranil Wickremesinghe contributed to the failure to act upon warnings about the attacks. Wickremesinghe said that there had been a “breakdown in communication.”
Islamic State claimed responsibility for the bombings.