Fifteen people, including six children, have died during a Sri Lankan security forces operation in the aftermath of the Easter attacks, as three cornered suicide bombers blew themselves up and others were shot dead, police said Saturday.

The three men set off explosives, also killing three women and six children inside what was believed to a bomber safe house near the eastern town of Kalmunai on Friday night.

"Three other men, also believed to be suicide bombers, were found dead outside the house," police said in a statement, adding that they had been shot.

Police backed by troops exchanged fire with those inside the house for over an hour, a military official said, adding that the bodies were recovered early Saturday following a search operation.

Security forces have stepped up their searches for extremists after the Daesh terror group claimed responsibility for the suicide attacks on three churches and three luxury hotels, which killed least 253 people and wounded hundreds more.

The joint operation between the police and the army was carried out following a tip-off that those responsible were holed up in a built-up area of Kalmunai, 370 kilometers (230 miles) east of the capital.

There were no casualties among the security forces, the police said.

The government has admitted major intelligence lapses, although Prime Minister Ranil Wickremesinghe said he was unaware of any warnings ahead of the attacks, in a sign of the rift between him and President Maithripala Sirisena.

"If we had any inkling, and we had not taken action, I would have handed in my resignation immediately," he told the BBC.

"But what do you do when you are out of the loop?"

Wickremesinghe tried to sack Sirisena last year, and experts believe the feud could have played a part in Sri Lanka's failure to act on intelligence warnings given weeks before the attacks.

Studio raided

Friday's clashes came hours after the security forces raided a nearby location where they believe militants recorded a video pledge to Daesh leader Abu Bakr al-Baghdadi before carrying out the Easter bombings.

Police said they found a Daesh flag and uniforms similar to those worn by the eight fighters for the video before they launched the attacks. Daesh released the video two days after the attacks.

The head of a local militant group, Zahran Hashim, who appeared in the video, was killed at one of the Colombo hotels targeted, the Shangri-La. He was accompanied by a second bomber identified as Ilham Ibrahim.

Authorities had been desperately searching for Hashim after naming his group, National Thowheeth Jama'ath (NTJ), as the perpetrators of the attack, but announced Friday he had been killed in the hotel bombing.

DNA tests are being done on a severed head to conclusively establish that it is Hashim's, officials said.