Sri Lankan authorities on Thursday revised the toll from Easter bombings down to 253, from the previous figure of 359, explaining that some of the badly mutilated bodies had been double-counted.

The health ministry said medical examiners had completed all autopsies by late on Thursday, and had concluded that several victims killed in the series of attacks had been counted more than once.

The official toll released by the police was reduced by 106 after the reconciliation of autopsy and DNA reports, the ministry said in a statement.

Sri Lanka’s top defence official said on Thursday that security agencies had been working to stop militant attacks in the days before Easter Sunday bombings that killed 359 people, and he was resigning to take responsibility for the failure.

The suicide bomb attacks on three churches and four hotels exposed a significant intelligence failure, with warnings of strikes not acted on and accusations of feuds at the highest levels of government undermining security cooperation.

Police issued names and photographs of seven people, three of them women, wanted in connection with the attacks, as bomb scares and security sweeps kept the country on edge.

“We were working on that. All those agencies were working on that,” Defence Secretary Hemasiri Fernando told Reuters, referring to intelligence tips from India warning of imminent strikes that came in over the days before the blasts.

Fernando, the top civil servant at the government’s defence department, said he had resigned to take responsibility for institutions he was in charge of, though he added there had been no failure on his part.

The Daesh group claimed responsibility for the coordinated attacks. If that connection is confirmed, it looks likely to be the deadliest ever such attack linked to the group.

Most of the victims were Sri Lankans, although authorities have said at least 38 foreigners were also 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. About 500 people were wounded.

Britain on Thursday warned its nationals to avoid the country unless it was absolutely necessary as there could be more attacks.

The Foreign Office said these could be indiscriminate, including in places visited by foreigners.

“Terrorists are very likely to try to carry out attacks in Sri Lanka,” it said in its updated travel advice.

Authorities have focused their investigations on international links to two domestic hardliner groups — National Thawheed Jama’ut and Jammiyathul Millathu Ibrahim — they believe carried out the attacks.

Daesh released a video that showed eight men, all but one with their faces covered, standing under a black flag and declaring their loyalty to its leader, Abu Bakr Al Baghdadi.

The government said there were nine suicide bombers, eight of whom had been identified, and that one was a woman.

A picture has emerged of a group of nine well-educated, home-grown suicide bombers. Two of them were brothers, sons of a wealthy spice trader and pillar of the business community, a source close to the family said.

One studied in Britain and Australia. At least 76 people, including several foreigners, have been rounded up since Sunday, but police on Thursday for the first time identified seven people they were looking for and appealed to the public for help in finding them.

Photographs, apparently casual snapshots, posted with a wanted notice showed young bearded men, one with a cap, and three young women, all with head scarves.

Fears that more bombers are at large has kept Sri Lanka on edge all week.

Authorities locked down the central bank and shut the road to the capital’s airport for part of the day because of bomb scares as communal tension simmered.

Office workers in Colombo’s business district were asked to go home early, police said, to avoid vulnerable throngs of people at rush hour. City-centre restaurants were also shutting early.

Police also arrested three people and seized 21 locally made grenades and six swords during a raid in Colombo, a spokesman said. He did not give details or suggest that the raid was linked to the suicide bombings.

Agencies