The death comes two days after Australian university lecturer Kylie Moore-Gilbert was released from jail in Iran,in exchange for three Iranian men linked to a botched 2012 bomb plot in Bangkok.

Iranian authoritieshad detained Moore-Gilbert after discovering she was in a relationship with an Israeli citizen,sparking baseless claims that she was a spy for Israel. She was held for two years before she was released,and arrived back in Australia on Friday.

While no one claimed responsibility for Friday's attack,Iranian Foreign Minister Mohammad Javad Zarif pointed the finger at Israel,calling the killing an act of"state terror".

"Terrorists murdered an eminent Iranian scientist today. This cowardice – with serious indications of Israeli role – shows desperate warmongering of perpetrators,"Zarif wrote on Twitter.

Hossein Dehghan,an adviser to Iran's supreme leader and a presidential candidate in Iran's 2021 election,also blamed Israel – and issued a warning.

"In the last days of their gambling ally’s political life,the Zionists seek to intensify and increase pressure on Iran to wage a full-blown war,"Dehghan wrote,appearing to refer to Trump's last days in office."We will descend like lightning on the killers of this oppressed martyr and we will make them regret their actions!"

The attack comes just days before the 10-year anniversary of the killing of Iranian nuclear scientist Majid Shahriari that Tehran also blamed on Israel. That and other targeted killings happened at the time that the so-called Stuxnet virus,believed to be an Israeli and American creation,destroyed Iranian centrifuges.

The area around Absard,which has a view of Mount Damavand,the country's highest peak,is filled with holiday villas. Roads on Friday,part of the Iranian weekend,were emptier than normal due to a lockdown over the coronavirus pandemic,offering his attackers a chance to strike with fewer people around.

Fakhrizadeh led Iran's so-called AMAD program that Israel and the West have alleged was a military operation looking at the feasibility of building a nuclear weapon. Tehran long has maintained its nuclear program is only for civilian purposes.

The International Atomic Energy Agency says Iran"carried out activities relevant to the development of a nuclear explosive device"in a"structured program"through the end of 2003. That was the AMAD program,which included work on the carefully timed high explosives needed to detonate an implosion-style nuclear bomb.

Iran also"conducted computer modelling of a nuclear explosive device"before 2005 and between 2005 and 2009,the IAEA has said. The agency said,however,that those calculations were"incomplete and fragmented".

IAEA inspectors now monitor Iranian nuclear sites as part of the now-unravelling nuclear deal with world powers. Experts believe Iran has enough low-enriched uranium to make at least two nuclear weapons if it chose to pursue the bomb. Meanwhile,an advanced centrifuge assembly plant at Iran's Natanz nuclear facility exploded in July in what Tehran now calls a sabotage attack.

Fakhrizadeh,born in 1958,had been sanctioned by the UN Security Council and the US for his work on AMAD. Iran always described him as a university physics professor. A member of the Revolutionary Guard,Fakhrizadeh had been seen in pictures in meetings attended by Iran's Supreme Leader Ayatollah Ali Khamenei,a sign of his power.

In recent years,US sanctions lists name him as heading Iran's Organisation for Defensive Innovation and Research. The State Department described that organisation last year as working on"dual-use research and development activities,of which aspects are potentially useful for nuclear weapons and nuclear weapons delivery systems".

In 2018,Netanyahu gave a presentation in which he unveiled what he described as material stolen by Israel from an Iranian nuclear archive.

"A key part of the plan was to form new organisations to continue the work,"Netanyahu alleged."This is how Dr Mohsen Fakhrizadeh,head of Project Amad,put it. Remember that name,Fakhrizadeh."

AP,with Megan Levy