A drone attack on an Iranian military facility that resulted in a large explosion in the centre 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 US about the incident.

The facility’s purpose was not clear, and neither was how much damage the strike caused. But Isfahan is a major centre 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 US 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.