This still image obtained from an eyewitness footage shows what is said to be the moment of an explosion at a military site in Isfahan, Iran, on Jan 29, 2023. (PHOTO / POOL / WANA VIA REUTERS)

DUBAI - Iran blamed Israel for a drone attack on a military factory near the central city of Isfahan, the semi-official ISNA news agency said on Thursday, vowing revenge for what appeared to be the latest episode in a long-running covert war.

In a letter to the UN chief, Iran's UN envoy, Amir Saeid Iravani, said a "primary investigation suggested Israel was responsible" for Saturday night's attack, which Tehran had said caused no casualties or serious damage.

"Iran reserves its legitimate and inherent right to defend its national security and firmly respond to any threat or wrongdoing of the Zionist regime (Israel) wherever and whenever it deems necessary," Iravani said in the letter.

"This action undertaken by the Zionist regime (Israel) goes against international law."

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Iran reserves its legitimate and inherent right to defend its national security and firmly respond to any threat or wrongdoing of the Zionist regime (Israel) wherever and whenever it deems necessary ... This action undertaken by the Zionist regime (Israel) goes against international law.

Amir Saeid Iravani, Iran's UN envoy

Israel has long said it is willing to strike Iranian targets if diplomacy fails to curb Tehran's nuclear or missile programs, but does not comment on specific incidents.

Talks between Iran and world powers to revive a 2015 nuclear deal have stalled since September. Under the pact, abandoned by Washington in 2018 under then-president Donald Trump, Tehran agreed to limit nuclear work in return for easing of sanctions.

Iran accused Israel in the past of planning attacks using agents inside Iranian territory.

In July, Tehran said it had arrested a sabotage team of Kurdish militants working for Israel who planned to blow up a "sensitive" defense industry center in Isfahan.

"The equipment and explosives used in the Isfahan attack were transferred into Iran with the help of anti-revolutionary groups based in Iraq's Kurdistan region under orders by a foreign security service," Iran’s Nournews reported on Wednesday.

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Several nuclear sites are located in Isfahan province, including Natanz, the centerpiece of Iran’s uranium enrichment program, which Iran accused Israel of sabotaging in 2021. There have been a number of explosions and fires around Iranian military, nuclear and industrial sites in recent years.