U.S. officials said Thursday the suicide bomber responsible for a deadly attack on Israeli vacationers in Bulgaria was a member of a Hezbollah cell that was operating in the country and looking for such targets, backing Israel’s assertions in new source of tension with Iran.

One senior American official told The New York Times the current intelligence assessment was that the bomber who struck Wednesday, killing five Israelis, had been “acting under broad guidance” to hit Israeli targets when opportunities presented themselves, and that the guidance came through to Hezbollah, the Lebanese Shia militant group, by Iran, its primary sponsor. Two other American officials confirmed that Hezbollah was behind the bombing, but declined to provide additional details.

The attacks, the official said, were in retaliation for the assassinations of Iranian nuclear scientists, for which Iran has blamed Israeli agents — an accusation that Israel has neither confirmed nor denied. “This was tit for tat,” said the American official, who spoke on condition of anonymity because the investigation was still in progress.

Bulgaria's Jews, who long felt secure, are suddenly feeling a chill.

“We used to convene without a shred of fear in the Jewish community’s buildings,” Kamen Petrov, vice president of Maccabi Bulgaria, told the Jewish Telegraphic Agency. “I guess we had been unprepared. Things will have to change from now on. We thought something like this could not happen in Bulgaria.”

Wednesday’s explosion outside Sarafovo Airport in Burgas killed six Israeli tourists, a Bulgarian bus driver and the suspected suicide bomber. More than 30 Israelis were injured. The Israelis had just arrived on a charter flight from Israel.

Maxim Benvenisti, president of the Organization of Jews in Bulgaria, said that three years ago the community had drafted contingency plans for potential terror attacks.

“We discussed such scenarios. But we see that it’s one thing to discuss them, and it’s another to see the scenario happening before your eyes,” he told JTA. Bevenisti said security measures will now be tightened. “The situation needs to be improved,” he said.

Bulgarian President Rosen Plevneliev said Wednesday that at a meeting a month ago, with representatives of the Mossad, Israel’s foreign intelligence service did not warn Bulgarian officials of the possibility of a terrorist attack.

Bulgaria’s Jewish community had increased its security arrangements in February, following warnings from the Israeli Embassy in Sofia, according to Martin Levi, vice chairman of the Jewish community in Sofia, Bulgaria’s capital. Among other measures, security at the entrances to the community building in Sofia and other Jewish institutions were tightened. Bulgarian authorities had been made aware of the warnings, he said.

That came in the wake of the discovery by Bulgarian authorities of a bomb on a charter bus for Israelis that was heading to a Bulgarian ski resort from the Turkish border.

“We took the alerts seriously and upped security, but the Bulgarian authorities were dismissive,” Levi said. “Some argued Bulgaria was immune because it had such excellent relations and cultural attachment to Muslim populations. I am deeply disappointed in how the authorities handled this.”

The New York Times Israel New York Israel