Iranian state television said on Friday that Mohsen Fakhrizadeh, a prominent nuclear scientist, had been "assassinated" in an ambush near Tehran.

State media reported that the physicist died in hospital of injuries sustained after armed assassins gunned him down in his car.

"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," a statement by Iran's armed forces carried by state media said. 

State TV cited sources confirming the death but did not provide any further details. The attack reportedly happened in the city of Absard.

Iran points finger at Israel

In a letter to UN Secretary-General Antonio Guterres and the UN Security Council, Iran's UN envoy Majid Takht Ravanchi said there were "serious indications of Israeli responsibility."

"Warning against any adventuristic measures by the United States and Israel against my country, particularly during the remaining period of the current administration of the United States in office, the Islamic Republic of Iran reserves its rights to take all necessary measures to defend its people and secure its interests," read part of the letter, which was seen by Reuters.

Iranian Foreign Minister Javad Zarif made similar comments earlier on Friday, tweeting that there was evidence Israel was involved.

"Terrorists murdered an eminent Iranian scientist today. This cowardice — with serious indications of Israeli role — shows desperate warmongering of perpetrators," he wrote.

"In the last days of the political life of their ... ally (US President Donald Trump), the Zionists (Israel) seek to intensify pressure on Iran and create a full-blown war," top Iranian military commander Hossein Dehghan tweeted.

Israel declines to comment

Israeli Prime Minister Benjamin Netanyahu's office has said it would not comment on the attack. But revelations that Netanyahu once called out Fakhrizadeh's name in a news conference, saying "remember that name" has fueled speculation of the country's involvement.

Questions over who was responsible

Referring to the rumors, Trita Parsi, executive vice president of US think-tank The Quincy Institute for Responsible Statecraft, told DW that "not that many" countries have "the capacity, the intent and the motivation" to carry out an operation of this kind, other than Israel and the US.

He warned that retaliation by Iran would almost be a "win-win situation" for Israel and that Prime Minister Netanyahu "has been looking for quite some time" for a fight with Tehran.

Speculation has been building since US President Donald Trump's election defeat of a planned US-Israeli strike on Iran before he leaves office, which could possibly lead to a full-scale war, and which Parsi said would be "absolutely devastating for the region as a whole."

"This is not Iraq. this is not Afghanistan. It's going to be much, much worse," he warned.

Prepare for 'strong reaction'

Another Iran expert, Cornelius Adebahr from the German Council of Foreign Relations, told DW that the world can expect a "strong reaction" from Iran to the assassination

"Iran will be pressed to retaliate. There will be domestic pressure in Iran and at the same time, it will be hard for the United States or any other major power to make any concessions to Iran if it is seen as retaliating against regional adversaries," he said.

Read more: Germany hosts France, Britain for talks on Iran nuclear deal

Ex-CIA chief condemns 'criminal act'

Former CIA director John Brennan warned that the killing could spark a wider problem in the Middle East.

"This was a criminal act and highly reckless. It risks lethal retaliation and a new round of regional conflict," tweeted Brennan.

Ellie Geranmayeh of the European Council on International Relations tweeted the "objective behind the killing wasn't to hinder [Iran's] nuclear programme but to undermine diplomacy."

She added that recent high-level visits by the US to Israel and Saudi Arabia "raised flags something being cooked up" that could potentially "complicate" diplomatic efforts by incoming US President-elect Joe Biden.

Leader of nuclear program 'Hope'

Fakhrizadeh led a nuclear program called "Amad" or "Hope" that was disbanded in the 2000s. Israel and the West alleged it was a military operation, but Tehran has long said that all its nuclear activities are peaceful.

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. The power has more recently been accused of stockpiling 10 times the amount of uranium agreed in a precarious nuclear deal.

ed,tj,kbd/rs (AP, dpa, AFP, Reuters)