A senior Iranian military commander has vowed to avenge the killing of Mohsen Fakhrizadeh, its top nuclear scientist who was killed in an ambush near Tehran on Friday, Reuters reported.

“We will strike as thunder at the killers of this oppressed martyr and will make them regret their action,” Hossein Dehghan, the military advisor to Supreme Leader Ayatollah Ali Khamenei, said.

Iran has blamed Israel for the killing. “This cowardice – with serious indications of Israeli role – shows desperate warmongering of perpetrators,” Iran’s Foreign Minister Javad Zarif said. “Iran calls on int’l [international] community– and especially EU [European Union]– to end their shameful double standards & condemn this act of state terror.”

Israeli Prime Minister Benjamin Netanyahu had specifically mentioned Fakhrizadeh during his presentation on Iran’s nuclear programme, reported BBC. “Remember that name,” Netanyahu had said as he identified Fakhrizedeh. However, Isreal has so far not issued a statement on the allegations.

Western intelligence agencies believe the killed scientist was behind a covert nuclear weapons programme, although Iran says its nuclear plan is meant for peaceful purposes.

Speaking on the killing, Iran’s UN ambassador Majid Takht Ravanchi said it was a clear violation of international law meant to wreak havoc in the region.

Major General Hossein Salami, the commander of the Islamic Revolutionary Guard Corps, said the “assassination of nuclear scientists is the most obvious violation of the global hegemony to prevent our access to modern sciences”.

Former chief of the United States’ Central Intelligence Agency John Brennan also condemned the killing. In a series of tweets, Brennan said that it was a “highly reckless act” that could lead to “lethal retaliation” and fresh conflict in the region.

“I do not know whether a foreign government authorized or carried out the murder of Fakhrizadeh,” he said. “Such an act of state-sponsored terrorism would be a flagrant violation of international law & encourage more governments to carry out lethal attacks against foreign officials.”

The former CIA chief also advised Iran to avoid retaliating to the perceived culprits, asking the country to wait for a “responsible American leadership on the global stage”. President-elect Joe Biden has said that he would reengage with Iran despite opposition from Israel.

On Friday, Iran’s defence ministry said in a statement that Armed terrorists targeted a vehicle carrying Fakhrizadeh. The terrorists reportedly “blew up another car” before firing on a vehicle carrying Fakhrizadeh and his bodyguards in the ambush.

Fakhrizadeh, 59, has long been described by Western countries as a leader of a covert atomic bomb programme halted in 2003, which Israel and the United States accuse Tehran of trying to restore in secret, according to Reuters. Iran has long denied seeking to weaponise nuclear energy.

Fakhrizadeh was the only Iranian scientist named in the International Atomic Energy Agency’s 2015 “final assessment” of open questions about Iran’s nuclear programme. He had long been the top target of the Mossad, Israel’s intelligence service, reported The New York Times.