A little-known Islamist group, Jamaat al-Tawhid al-Watania has claimed responsibility for the bomb attacks carried out in churches and hotels in the Sri Lanka capital on Easter Sunday.
The Al-Arabiya TV channel said on Twitter on Monday without providing any details about the group, Russian news agency TASS reported.
A total of eight explosions hit luxury hotels and churches in the cities of Colombo, Negombo and Batticaloa during Easter services.
Sri Lanka said on Monday it was invoking emergency powers in the aftermath of devastating attacks, blamed on militants with foreign links, in which 290 people were killed and nearly 500 wounded.
The emergency law, which gives police and the military extensive powers to detain and interrogate suspects without court orders, will go into effect at midnight on Monday, the president's office said.
Colombo, the seaside capital of the Indian Ocean island, was jittery on Monday. Police said 87 bomb detonators were found at the city's main bus station, while an explosive went off near a church where scores were killed on Sunday when bomb squad officials were trying to defuse it.
Investigators said seven suicide bombers took part in the attacks while a government spokesman said an international network was involved.
Police had received a tip-off of a possible attack on churches by a little-known domestic Islamist group some 10 days ago, Reuters reported citing an official document.
The intelligence report, dated Apr 11 and seen by Reuters, said a foreign intelligence agency had warned authorities of possible attacks on churches by the leader of the group, the National Thawheed Jama'ut. It was not immediately clear what action, if any, was taken on the tip-off.
Police said 24 people had been arrested, all of whom were Sri Lankan, but they gave no more details.