Iran on Thursday blamed Israel for a drone attack that targeted a military workshop in its central city of Isfahan over the weekend, warning it “reserves its legitimate and inherent right” to retaliate.

Iran’s mission to the United Nations, in a letter it published on its website, attributed the attack late Saturday to Israel.

“Early investigations suggest that the Israeli regime was responsible for this attempted act of aggression,” the letter signed by Iranian ambassador Amir Saeid Iravani said. The letter did not elaborate on what evidence supported Iran’s suspicion.

Israeli officials declined to comment. However, Israel has carried out a series of attacks targeting Iran’s nuclear program and other sites since the collapse of its 2015 nuclear deal with world powers as part of a yearslong shadow war between the Mideast rivals.

Details on the Isfahan attack, which happened around 11:30 p.m. Saturday, still remain scarce days after the assault. A Defense Ministry statement described three drones being launched at the facility, with two of them successfully shot down. A third apparently made it through to strike the building, causing “minor damage” to its roof and wounding no one, the ministry said.

Iran’s state-run IRNA news agency later described the drones as “quadcopters equipped with bomblets.” Quadcopters, which get their name from having four rotors, typically operate from short ranges by remote control. Iranian state television later aired footage of debris from the drones, which resembled commercially available quadcopters.

It remains unclear what the workshop produced. Iravani referred to it only as a “a workshop complex of the Iranian Defense Ministry” in his letter.

Israel had been initially suspected as possibly being behind the attack. Iran’s Intelligence Ministry in July claimed to have broken up a plot to target sensitive sites around Isfahan.

A segment aired on Iranian state television in October included purported confessions by alleged members of Komala, a Kurdish opposition party that is exiled from Iran and now lives in Iraq, that they planned to target a military aerospace facility in Isfahan after being trained by Israel’s Mossad intelligence service. However, activists say Iran has aired hundreds of coerced confession on state TV over the last decade.

Iravani’s letter to U.N. Secretary-General Antonio Guterres and the Security Council warned Tehran could respond to the attack.

“The Islamic Republic of Iran reserves its legitimate and inherent right ... to defend its national security and respond resolutely to any threats or wrongful actions by the Israeli regime, wherever and whenever deemed necessary,” the letter read.

Israeli officials rarely acknowledge operations carried out by the country’s secret military units or its Mossad intelligence agency. However, Israeli Prime Minister Benjamin Netanyahu, who recently re-entered the premiership, long has considered Iran to be the biggest threat his nation faces.

Iravani’s letter separately complained about Mykhailo Podolyak, an adviser to Ukrainian President Ukrainian President Volodymyr Zelenskyy, tweeting after the drone attack: “Explosive night in Iran ... Ukraine had warned you.” Iran has supplied Russia with bomb-carrying drones that Moscow has used to target power plants and civilian sites in Ukraine in its war on the country.

AP