Fifteen people including six children have died during a Sri Lankan security forces operation on an ISIS hideout 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 jihadist 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 ISIS 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 (230 miles) east of the capital.

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

According to a report in AFP, at least 94 people are in custody, including a man believed to be the father of two of the bombers. Police said another 20 people were detained overnight.

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?”

Prime Minister Ranil Wickremesinghe was kept out of intelligence briefings since he fell out with the president.

The President had fired the Prime Minister last year but was forced to reinstate him after a furore and a judicial order.

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

Police said they found an ISIS flag and uniforms similar to those worn by the eight fighters for the video before they launched the attacks. ISIS released the video two days after the attacks. They also found 150 sticks of gelignite, thousands of steel pellets and a drone camera.

Meanwhile, an Islamic extremist Zahran Hashim believed to have played a key role in Sri Lanka’s deadly Easter bombings died in an attack on a Colombo hotel, the country’s president confirmed Friday.

Security forces had been on a desperate hunt for Hashim, believed to be around 40 after the government named the group he led — the National Thowheeth Jama’ath — as its prime suspect.

His appearance in the ISIS video, where he is seen leading a group of seven others in a pledge of allegiance to ISIS chief Abu Bakr al-Baghdadi, only heightened fears about the radical.

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

Earlier on Tuesday, the Islamic State or the ISIS had claimed responsibility for the deadly attacks without providing any major evidence.

India is learnt to have sent as many as three alerts before the deadly bombings in Sri Lanka.

The blasts targeted St Anthony’s Church in Colombo, St Sebastian’s Church in the western coastal town of Negombo and Zion Church in the eastern town of Batticaloa around 8.45 am (local time) as the Easter Sunday mass were in progress.

Explosions were also reported from three five-star hotels — the Shangri-La, the Cinnamon Grand and the Kingsbury in Colombo.

(With inputs from AFP)