Daesh claimed responsibility for three men who blew themselves up in clashes with Sri Lankan police, the militant group said in a statement.
The men set off explosives after an hour-long gun battle with police Saturday, inside what was believed to be a terrorist hideout near the eastern town of Kalmunai, in the latest fallout from the Easter attacks.
In a statement posted Saturday by the Daesh propaganda unit the Amaq News Agency, Daesh said the three men were part of the Daesh group and detonated their bombs after the fight with police.
The statement said the men "clashed with them (Sri Lankan police) with automatic weapons, and after exhausting their ammunition, detonated on them their explosive belts."
Fifteen people died in the clashes, police said, including three women and six children.
The violence came six days after the Easter Day bombings on three churches and three luxury hotels which killed at least 253 people and injured 500.
Security forces armed with emergency powers have stepped up search operations for Islamic extremists since the bombings.
Kalmunai is in the same region as the home town of the terrorist Zahran Hashim who founded the group accused of staging the attacks.
A girl and a woman have survived a fiery explosion at a suspected militant safe house in eastern Sri Lanka that killed 15 people during a raid linked to the Easter bombings.
Police spokesman Ruwan Gunasekara said Saturday that the woman and girl are critically injured and are being treated at a nearby hospital in Ampara District.
Sri Lankan security forces have been clearing the safe house following a Friday night gunbattle between soldiers and suspected militants. Authorities say the militants set off three explosions and opened fire.
Police say they found 15 bodies including six children at the house.
Pictures by The Associated Press show the charred remains of one child. The body of another child can be seen in a green T-shirt with the words "good boy" written on the back.
The bodies of an adult woman and man were found after the explosion with their clothes burned off.
The bodies of 15 people, including six children, were discovered at the site of a fierce overnight gun battle on the eastern coast of Sri Lanka, a military spokesman said on Saturday, six days after a rash of suicide bomber attacks that killed more than 250 people.
Suicide bombers blew themselves up when cornered by security forces in eastern Sri Lanka, police said on Saturday.
Three men set off explosives killing three other women and six children inside what was believed to a safe house near the town of Kalmunai on Friday night, police said.
"Three other men, also believed to be suicide bombers, were found dead outside the house," police said in a statement.
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.
Gunmen opened fire on troops when they attempted to storm the house under cover of darkness, military spokesman Sumith Atapattu said, adding that a civilian had got caught in the crossfire and died.
The joint operation was carried out following a tip-off that those responsible for the Easter suicide bombings 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 clashes came hours after the security forces raided a nearby location where they believe radicals recorded a video pledge to Daesh leader Abu Bakr Al Baghdadi before carrying out the deadly 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 Sunday's attacks against three luxury hotels and three churches, killing 253.
"We have found the backdrop the group used to record their video," the police said in an earlier statement on Friday night.
Daesh released the video two days after the attack.
Police showed the clothing and the flag on national television, as well as some 150 sticks of dynamite and about 100,000 ball bearings seized from the house.
Security forces armed with emergency powers have stepped up search operations for extremists responsible for the bombings.