Iran's president on Saturday accused Israel of killing a prominent Iranian scientist long suspected by the West of masterminding a secret nuclear bomb programme, state TV reported.
Iran's clerical and military rulers have threatened revenge for Friday's killing of Mohsen Fakhrizadeh, who Iranian media said died in hospital after assassins gunned him down in his car near Tehran.
"Once again, the evil hands of global arrogance were stained with the blood of the mercenary usurper Zionist regime," President Hassan Rouhani said in a statement, according to state TV.
Iran generally uses the term "global arrogance" to refer to the United States.
"The assassination of martyr Fakhrizadeh shows our enemies' despair and the depth of their hatred... His martyrdom will not slow down our achievements." He then offered condolences to "the scientific community and the revolutionary people of Iran."
He added that Tehran will retaliate for the alleged assassination in due time. "Our people are wiser than to fall in the trap of the Zionist regime ... Iran will surely respond to the martyrdom of our scientist at the proper time," he said.
Fakhrizadeh was "seriously wounded" when assailants targeted his car before being engaged in a gunfight with his bodyguards in an attack outside Tehran, Iran's defense ministry said. It added that Fakhrizadeh, who headed the ministry's reasearch and innovation organisation, was later "martyred" after medics failed to revive him.
The New York Times said an American official and two other intelligence officials confirmed Israel was behind the attack, without giving further details.
The death of Fakhrizadeh could provoke confrontation between Iran and its foes in the last weeks of Donald Trump's U.S. presidency while complicating any effort by President-elect Joe Biden to revive the detente of Barack Obama's presidency.