A wave of bombings that killed 290 people in Sri Lanka on Sunday was carried out with the support of an international network, officials said.
The government has blamed a little-known local jihadist group, National Thowheed Jamath, although no-one has yet admitted carrying out the bombings.
Another 500 people were injured in the suicide attacks on churches and hotels.
Police arrested 24 people in a series of raids and the president’s office declared a state of national emergency.
The emergency declaration, which comes into effect from midnight (18:30 GMT) on Monday, will give police and military extensive powers to detain and interrogate suspects without court orders.
On Monday, another blast rocked a street near a church in the capital, Colombo. Police were attempting to defuse explosives in a vehicle used by the attackers when it blew up. It is not yet known if anyone was hurt.
Sri Lankan authorities were warned about a bomb threat from National Thowheed Jamath a full two weeks before the attacks, cabinet spokesman Rajitha Senaratne said at a press conference.
He said that the warnings were not passed on to the Prime Minister, Ranil Wickremesinghe, or his cabinet. Mr Wickremesinghe acknowledged that security services had been “aware of information” but had not acted on the information