COLOMBO: Sri Lankan authorities on Monday (Apr 22) ordered a state of emergency to be introduced following the deadly Easter attacks, the president's office said.
The special measures were being brought in "to allow the police and the three forces to ensure public security", the statement said, referring to the army, navy and air force.
A first curfew had been ordered shortly after the blasts ripped through Sri Lanka, with social media access, including Facebook and WhatsApp, curbed to restrict “wrong information” from spreading.
This initial curfew was lifted on Monday morning, but a second curfew - running from 8pm on Monday to 4am on Tuesday - was imposed.
READ: "People screaming, dead bodies all around" - Survivor recalls chaos during deadly Sri Lanka blasts
Cabinet minister Rajitha Senaratne said that the government was investigating whether a local extremist group, called the National Thowheeth Jama'ath (NTJ), was behind the blasts and if it had "international support".
"We don't see that only a small organisation in this country can do all that," said Mr Senaratne.
"We are now investigating the international support for them, and their other links ... how they produced the suicide bombers here, and how they produced bombs like this."
Officials said President Maithripala Sirisena would meet with Colombo-based diplomats on Tuesday to seek international assistance as part of the investigation.
"The intelligence sections have reported that there are international terror groups which are behind the local terrorists," the statement added. "International assistance will be sought to combat them."
Documents seen by AFP show Sri Lanka's police chief issued a warning on Apr 11, saying that a "foreign intelligence agency" had reported NTJ was planning attacks on churches and the Indian high commission.
Not much is known about the NTJ, a radical group that has been linked to the vandalising of Buddhist statues.
A police source told AFP that all 24 people in custody in connection with the attacks belong to an "extremist" group, but did not specify further.
Sri Lankans accounted for the bulk of those killed or injured, although government officials said 32 foreigners were also killed. These included British, US, Turkish, Indian, Chinese, Danish, Dutch, Portuguese and Japanese nationals.
On Apr 25, the Sri Lankan government revised the death toll to 253.