A gun battle between troops and suspected Islamist militants on Sri Lanka’s east coast left 15 dead, including six children, a military spokesman said yesterday, six days after suicide bombers killed more than 250 people on the island.

The shootout at a safe house erupted on Friday in Sainthamaruthu in Ampara district, to the south of the Sri

Lankan town of Batticaloa, site of one of the Easter Sunday blasts which have been claimed by Islamic State.

The government has said that the attacks on three churches and four hotels, most of which were in the capital Colombo, were carried out by nine well-educated Sri Lankans, eight of whom have been identified.

A police spokesman said three suspected suicide bombers were among the dead following Friday’s gun battle.

Authorities have warned there could be more attacks against religious centres following the bombings, which shattered the relative calm in Buddhist-majority Sri Lanka since a conflict with mostly-Hindu ethnic Tamil separatists ended a decade ago.

President Maithripala Sirisena and the government headed by Prime Minister Ranil Wickremesinghe have faced criticism over the attacks about which there were repeated warnings from India.

Both have said intelligence was not shared with them, exposing rifts at the top of the government and raising questions about its ability to deal with the security crisis.

Two sources told Reuters on Saturday that Sri Lanka’s police chief had refused to accept Sirisena’s request to step down, in a further embarrassment for the president.

The US State Department, warning that terrorist groups were continuing to plot attacks, urged citizens to reconsider travel to Sri Lanka and ordered the departure of all school-age family members of US government employees. It also authorised non-emergency employees to leave.

Britain has also warned its nationals to avoid travelling to Sri Lanka unless absolutely necessary.

The east coast battle broke out when troops heading towards a suspected militant safe house were repulsed by three explosions and gunfire, military spokesman Sumith Atapattu said.

“Troops retaliated and raided the safe house where a large cache of explosives had been stored,” he said in a statement, adding that the militants were suspected members of the domestic Islamist group National Towheed Jama’at (NTJ), which has been blamed for last Sunday’s attacks.

Bomb-making materials, dozens of gelignite sticks and thousands of ball bearings were found in a search of a separate house in the same area along with Islamic State banners and uniforms, the military said.

Police said on Friday they were trying to track down 140 people they believe have links with Islamic State, while Sri Lanka’s president said some Sri Lankan youths had been involved with it since 2013 and that there were drug trafficking links.

“Our efforts to eradicate the drugs menace from the country could have advanced the ISIS attack,” Sirisena said.

Nearly 10,000 soldiers have been deployed across the Indian Ocean island state to carry out searches and provide security for religious centres, the military said.

Authorities have so far focused their investigations on international links to two domestic groups they believe carried out the attacks, NTJ and Jammiyathul Millathu Ibrahim.

They said they have detained at least 76 people, including foreigners from Syria and Egypt, with 20 arrested in the past 24 hours alone.

In a separate raid on a mosque in Colombo, a suspect was arrested and a haul of 40 swords and kris knives were seized from under the bed of the chief cleric, police said.

Islamic State provided no evidence that it was behind Sunday’s blasts, which would be one of the worst attacks carried out by the group outside Iraq and Syria.

The group released a video showing eight men, all but one with their faces covered, under a black Islamic State flag and declaring their loyalty to its leader, Abu Bakr Al-Baghdadi.

Muslims were urged to pray at home on Friday after the State Intelligence Services warned of possible car bomb attacks, amid fears of retaliatory violence. Many have fled their homes amid bomb scares, lockdowns and security sweeps.

Archbishop of Colombo Cardinal Malcolm Ranjith told reporters he had seen an internal security document warning of further attacks on churches and said there would be no Catholic masses this Sunday anywhere on the island.

Sri Lanka’s 22 million people include minority Christians, Muslims and Hindus. Until now, Christians had largely managed to avoid the worst of the island’s conflict and communal tensions.

Most of the victims of the Easter Sunday suicide bombings were Sri Lankans, although authorities said at least 40 foreigners were killed, many of them tourists sitting down to breakfast at top-end hotels when the bombers struck.

They included British, US, Australian, Turkish, Indian, Chinese, Danish, Dutch and Portuguese nationals.