Mohsen Fakhrizadeh, Iran’s most senior nuclear scientist, was assassinated on Friday near the capital Tehran. Iran’s Foreign Minister Mohammad Javad Zarif condemned the killing “as an act of state terror”.
Mr Fakhrizadeh’s car was reportedly hit by an explosion set off by a “suicide” assassin before being struck with bullets.
Several other people also died in the incident, according to state media.
In a statement, Iran’s armed forces said: “Unfortunately, the medical team did not succeed in reviving him, and a few minutes ago, this manager and scientist achieved the high status of martyrdom after years of effort and struggle.”
Mr Fakhrizadeh was a senior officer of the elite Islamic Revolutionary Guards Corps and one of the most renowned Iranian nuclear scientists.
Iran said it would “strike like thunder” on whoever carried out the attack.
A top Iranian military adviser, Hossein Dehghan, tweeted: “We will strike as thunder at the killers of this oppressed martyr and will make them regret their action”.
It comes amid continuing tensions in the Middle East between Iran and the US with its allies Israel and Saudi Arabia.
Western intelligence agencies reportedly believe Mr Fakhrizadeh was involved in a covert Iranian nuclear weapons programme.
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US President Donald Trump also appeared to acknowledge the assassination after he retweeted a New York Times article about Mr Fakhrizadeh’s death.
A spokesperson for the Israeli military told The Guardian: “We don’t comment on reports in the foreign media.”
No group is yet to claim responsibility for Mr Fakhrizadeh’s death.
But the assassination came just a few days after Israel’s Defence Forces had reportedly been told to prepare for a US military strike against Iran before Mr Trump leaves office.
President Trump has spoken about the possibility of a final Iran strike with senior security officials, according to the New York Times.
But the US president was believed to have been “talked out” of hitting the Islamic republic after officials warned him it could trigger a regional war.
US President-elect Joe Biden has pledged to re-engage with Iran when he takes office in January despite opposition from Israel.
A dramatic move in the Middle East by Mr Trump in the final weeks of his presidency could create geopolitical problems for Mr Biden.
The President-elect has already vowed to revive the 2015 Nuclear Deal which would be a reversal of Mr Trump’s “maximum pressure” policy.
The Israeli Defence Force have reportedly been on high alert in recent weeks in preparation for a possible US military strike.