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.
Sri Lankans accounted for the bulk of the 290 people killed and 500 wounded, although government officials said 32 foreigners were also killed. These included British, U.S., Turkish, Indian, Chinese, Danish, Dutch and Portuguese nations.
A British mother and son eating breakfast at the luxury Shangri-La hotel were among those killed, Britain’s The Telegraph newspaper reported.
One Australian survivor, identified only as Sam, told Australia’s 3AW radio the hotel was a scene of “absolute carnage”.
He said he and a travel partner were also having breakfast at the Shangri-La when two blasts went off. He said he had seen two men wearing backpacks seconds before the blasts.
“There were people screaming and dead bodies all around,” he said. “Kids crying, kids on the ground, I don’t know if they were dead or not, just crazy.”
There were similar scenes of carnage at two churches in or near Colombo, and a third church in the northeast town of Batticaloa, where worshippers had gathered for Easter Sunday services. Pictures from the scene showed bodies on the ground and blood-spattered pews and statues.
Dozens were killed in one of the blasts at the Gothic-style St. Sebastian church in Katuwapitiya, north of Colombo. Police said they suspected that blast was a suicide attack.
Three police officers were also killed when security forces raided a house in Colombo several hours after the attacks.
Police reported an explosion at the house.