TEL AVIV — A drone attack on an Iranian military facility that resulted in a large explosion in the center of the city of Isfahan on Saturday was the work of the Mossad, Israel’s premier intelligence agency, according to senior intelligence officials who were familiar with the dialogue between Israel and the United States about the incident.
The facility’s purpose was not clear, and neither was how much damage the strike caused. But Isfahan is a major center of missile production, research and development for Iran, including the assembly of many of its Shahab medium-range missiles, which can reach Israel and beyond.
Weeks ago, American officials publicly identified Iran as the primary supplier of drones to Russia for use in the war in Ukraine, and they said they believed Russia was also trying to obtain Iranian missiles to use in the conflict. But U.S. officials said they believed this strike was prompted by Israel’s concerns about its own security, not the potential for missile exports to Russia.
The strike came just as Secretary of State Antony J. Blinken was beginning a visit to Israel, his first since Benjamin Netanyahu returned to office as prime minister. The director of the Central Intelligence Agency, William J. Burns, visited Israel last week, though it is not clear anything about the operation in Isfahan was discussed.
American officials quickly sent out word on Sunday morning that the United States was not responsible for the attack. One official confirmed that it had been conducted by Israel but did not have details about the target. Sometimes Israel gives the United States advance warning of an attack or informs American officials as an operation is being launched. It is unclear what happened in this case.
Isfahan is the site of four small nuclear research facilities, all supplied by China many years ago. But the facility that was struck on Saturday was in the middle of the city and did not appear to be nuclear-related.
Iran made no effort to hide the fact that an attack had happened, but said it had done little damage. In statements, senior Iranian officials contended that the drones — apparently quadcopters, a kind of aircraft with four separate propellers — had all been shot down.
Iran’s official news agency, IRNA, reported on Sunday that the drones had targeted an ammunition manufacturing plant, and that they had been shot down by a surface-to-air defense system. It is not clear why Iran would build an ammunition production plant in the middle of a city of roughly two million people.
Iran’s foreign minister, Hossein Amir Abdollahian, said at a news conference in Tehran on Sunday that “a cowardly drone attack on a military site in central Iran will not impede Iran’s progress on its peaceful nuclear program.”
This is Israel’s first known attack inside Iran since Mr. Netanyahu reassumed office, and it may indicate that he has adopted the strategy formed under his two predecessors and political rivals, Naftali Bennett and Yair Lapid, who expanded Israeli attacks inside Iran.
The quadcopters have become a signature of such operations.
In August 2019, Israel sent an exploding quadcopter into the heart of a Hezbollah-dominated neighborhood in Beirut, Lebanon, to destroy what Israeli officials described as machinery vital to the production of precision missiles.
In June 2021, quadcopters exploded at one of Iran’s main manufacturing centers for centrifuges, which purify uranium at the country’s two major uranium enrichment facilities, Fordow and Natanz. That attack was in Karaj, on the outskirts of Tehran. Iran claimed that there was no damage to the site, but satellite images showed evidence of significant damage.
A year ago, six quadcopters exploded at Kermanshah, Iran’s main manufacturing and storage plant for military drones.
And in May 2022, a drone strike targeted a highly sensitive military site outside Tehran where Iran develops missile, nuclear and drone technology.
The targets — presumably including the military facility in Isfahan — have been chosen in part to shake the Iranian leadership, because they demonstrate intelligence about the locations of key sites, even those hidden in the middle of cities.
But the strikes also reflect a change in Israeli strategy made after Mr. Bennett became prime minister in June 2021. He lasted a year in the post.
Mr. Bennett says in a forthcoming YouTube video shared with The New York Times that he decided to “create a price tag” and strike inside Iran in response to any attack on Israelis or Jews around the world. “The Iranians beat us, and soldiers die on the border,” Mr. Bennett says in the self-produced interview, while Iranian leaders “sit quietly in Tehran and we do nothing to them.”
It was not just the quadcopter attacks.
After “Iran tried to murder Israelis in Cyprus, in Turkey,” Mr. Bennett says, the Revolutionary Guards Corps commander behind it “was eliminated in Tehran.” He is referring to the assassination of Sayad Khodayee, who Israel claimed was a leader of a covert unit responsible for the abduction and killing of Israelis and other foreigners around the world.
After Israel adopted the new strategy, Mr. Bennett says in the video, President Biden, during a meeting, made a “sharp request” that Israel inform the United States in advance “of any action we take in Iran.”
Mr. Bennett refused, he says.
“There are things you do not want to know about in advance,” he recalls telling the American president.
The intelligence communities of Israel and the United States clashed on the issue in April 2021 after an operation by the Mossad to blow up bunkers at the Natanz enrichment site surprised the United States.
Mr. Burns called his counterpart at the Mossad at the time, Yossi Cohen, to express concern over the snub. Mr. Cohen said that the belated notification was the result of operational constraints and uncertainty about when the Natanz operation would take place.
Julian E. Barnes and Eric Schmitt contributed reporting.