The bodies of 15 people - including six children - have been found after a gun battle between Sri Lankan soldiers and suspected militants.
Authorities said the bodies of six men, three women and six children were recovered following a shootout and explosions in Kalmunai in the east of the country.
Police believe four suicide bombers were among the dead at what's thought to be a makeshift bomb factory.
Another woman and a child who were injured have been hospitalised.
The gun battle and explosions happened during a security operation linked to the Easter Sunday bombings.
The terrorist attacks left more than 250 people dead.
In a statement about the latest operation, the Sri Lankan government said: "Shooting erupted between security forces and a group of armed men during a search and cordon operation related to the Easter Sunday attacks.
"Four bodies suspected to be that of the suicide bombers have been recovered at the site of last night’s explosions and gun battles."
Separately, troops are also said to have found explosives, detonators, acid bottles, ISIS flags, suicide kits, military uniforms and more at a suspected safehouse for militants.
Investigations into last Sunday's attacks at churches and hotels in Sri Lanka are continuing.
Police said 20 more suspects were arrested over the past 24 hours in connection with the bombings.
With the country remaining on high alert, Sri Lankan Catholic leaders have taken the decision to cancel Sunday Masses tomorrow.
Islamic State has claimed responsibility for the attacks, although the country's government and security forces have come under intense scrutiny for failing to act on warnings about potential terrorist attacks.
A number of senior police and security officials have already been replaced in the wake of the bombings.
