Iran's most senior nuclear scientist Mohsen Fakhrizadeh has been assassinated near the capital Tehran, the country's defence ministry has confirmed.
Fakhrizadeh died in hospital after an attack in Absard, in Damavand county.
Iran's Foreign Minister Mohammad Javad Zarif, has condemned the killing "as an act of state terror".
Western intelligence agencies view Fakhrizadeh as being behind Iran's secret nuclear weapons programme.
He was reportedly described as the "father of the Iranian bomb" by diplomats.
Iran's most senior nuclear scientist assassinated near the capital Tehran, country's defence ministry says https://t.co/5Vm6V7eMcd
— BBC Breaking News (@BBCBreaking) November 27, 2020
News of the killing comes amid fresh concern about the increased amount of enriched uranium that Iran is producing. Enriched uranium is a vital component for both civil nuclear power generation and military nuclear weapons.
Iran insists its nuclear programme is exclusively for peaceful purposes.
Between 2010 and 2012, four Iranian nuclear scientists were assassinated and Iran has accused Israel of complicity in the killings.
Fakhrizadeh's name was specifically mentioned in Israeli PM Benjamin Netanyahu's presentation about Iran's nuclear programme in May 2018.
In a statement on Friday, Iran's defence ministry said: "Armed terrorists targeted a vehicle carrying Mohsen Fakhrizadeh, head of the ministry's research and innovation organisation.
"After a clash between the terrorists and his bodyguards, Mr Fakhrizadeh was severely injured and rushed to hospital.
"Unfortunately, the medical team's efforts to save him were unsuccessful and minutes ago he passed away."
Iranian media reports said the attackers opened fire on the scientist in his car.

Fars news agency earlier reported there was a car explosion in Absard town, with witnesses reporting that "three to four individuals, who are said to have been terrorists, were killed".
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