The bodies of 15 people, including six children, were discovered at the site of a fierce overnight gun battle in eastern Sri Lanka early Saturday (27 April), six days after suicide bombers killed 253 people.
The shootout between troops and suspected Islamist militants erupted near the town of Batticaloa, site of one of the Easter Sunday blasts at three churches and four luxury hotels.
A police spokesman said the shootout began when soldiers went to investigate a possible militant safe house and were fired upon and that three suspected suicide bombers were among the 15 dead.
The incident illustrates the tension that has gripped the country since the Easter Sunday bombings.
Raid on safe house led to gun battle
The militants were suspected members of the National Towheed Jama'at (NTJ), which has been blamed for last Sunday's attacks, military spokesman Sumith Atapattu said in a statement Saturday.
He said that three explosions were triggered as troops moved in on the militant safe house and gunfire began.
"Troops retaliated and raided the safe house where a large cache of explosives had been stored," he said.
Authorities ban two Islamist groups
President Maithripala Sirisena has banned the NTJ and another Islamist group suspected of being behind the Easter Sunday suicide bombings that killed more than 250 people, his office said on Saturday.
Authorities could not act earlier to ban the two little known groups because the law required them to show firm evidence against them, officials said.
Police 'seize explosives and ISIS flag'
In a separate raid conducted Friday in the eastern town of Sammanthurai, police said they seized explosives and a flag of so-called Islamic State (IS) in the house of one of the attackers.
It is also believed to be the house where the IS video claiming responsibility for the attack was shot.
The video released on Tuesday showed eight men, all but one with their faces covered, standing under a black IS flag and declaring their loyalty to its leader, Abu Bakr Al-Baghdadi.
Authorities say mastermind is dead
The man whose face could be seen in the video has been identified as Mohamed Zahran, a preacher from the east of Sri Lanka known for his militant views and Facebook posts who officials believe was the mastermind of the attack. He is believed to have been killed in the Shangri-La hotel attack.
Police said Friday they were trying to track down 140 people they believe have links with IS.
Police have detained at least 76 people, including foreigners from Syria and Egypt, in their investigations so far.
Fears of new attacks
Nearly 10,000 soldiers were deployed across the Indian Ocean island state to carry out searches and provide security for religious centres, the military said on Friday.
Muslims in Sri Lanka were urged to pray at home after the State Intelligence Services warned of possible car bomb attacks, amid fears of retaliatory violence.
Meanwhile, the US Embassy in Sri Lanka urged its citizens to avoid places of worship over the weekend after authorities reported there could be more attacks targeting religious centres.