"An unsuccessful attack was carried out using (drones) ... on one of the workshop complexes of the ministry of defence," it said, adding that the strike late Saturday night caused only minor damage to the roof of a building but no casualties.

The announcement of the attack comes at a tense time in Iran, which has been rocked by protests over the death of Mahsa Amini in September, tensions over its nuclear programme and accusations by some countries that Tehran has been supplying drones to Russia for the war in Ukraine.

The ministry said one of the drones was destroyed by the site's anti-aircraft defence system, while the other two exploded.

"The attack, which occurred around 11:30 pm on Saturday, did not cause any disruption to the operation of the complex," it said.

A video widely shared on social media, the authenticity of which AFP could not verify, shows a loud explosion at the site and images of emergency vehicles then heading towards the area.

The deputy governor of Isfahan province, Mohammad Reza Jan-Nesari, also said on television there had been "no casualties", adding that "the cause of the incident is under investigation."

Authorities did not elaborate on the activities at the targeted site, north of the city of Isfahan.

Iran has several known nuclear research sites in the region, including a uranium conversion plant.

In April 2021, Tehran announced that it had started producing 60 percent enriched uranium at the Natanz site in Isfahan province.

Negotiations to revive the 2015 nuclear deal, known by its acronym JCPOA, between Iran, the European Union and six major powers, stalled after the United States exited in 2018.

The agreement was aimed at preventing Tehran from acquiring atomic weapons, an objective that Iran has always denied pursuing.

In recent years, Iran has accused Israel of carrying out several covert actions on its soil, including an attack, according to Tehran, using a satellite-controlled machine gun, which killed a leading nuclear physicist, Mohsen Fakhrizadeh, in November 2020.

In addition, Tehran has been accused in recent months of supplying drones to Russia for the war in Ukraine, which Iran denies.