COLOMBO   -   At least 15 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 on Saturday.

The three men set off explosives, also killing three women and six children inside what was believed to be a militant 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 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 militant Islamic State (IS) 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 kilometres 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 British media. “But what do you do when you are out of the loop?”

Sirisena tried to sack Wickremesinghe 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.

Friday’s clashes came hours after the security forces raided a nearby location where they believe radicals recorded a video pledge to IS leader Abu Bakr al-Baghdadi before carrying out the bombings. Police said they found an IS flag and uniforms similar to those worn by the eight fighters for the video before they launched the attacks. IS released the video two days after the attacks.

The head of a local extremist 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 on 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.

Zahran Hashim, who is believed to have masterminded the Easter attacks in Sri Lanka, spent substantial time in southern India, said a top Sri Lankan military source, reported The Hindu.

Two days later, the militant Islamic State claimed responsibility for the attacks and subsequently released an image of eight suspected bombers. The man seen standing at the centre is believed to be Hashim. The other militants had covered their faces with a scarf.

Sri Lankan investigators, however, have identified nine suicide bombers, including a woman. “We are looking into the Islamic State angle. We also suspect that some of those radical youth were indoctrinated and trained in India, possibly Tamil Nadu,” the senior official said, on condition of anonymity. Indian officials would not comment on Hashim travelling to India but pointed to evidence of virtual links he maintained with youth believed to be of Indian origin. More than 100 followers of Hashim’s Facebook page are being investigated, said an official, who asked not to be named. The first hints of Hashim’s doctrinal videos, to likely radicalise youth, emerged when Indian authorities interrogated seven members of a group whose leader, officials found, was a follower of Hashim.

The men were Islamic State sympathisers and arrested in September 2018 in Coimbatore, on suspicion that they were plotting the assassination of certain political and religious leaders in India, the official said.