Iran's Judiciary Chief Ayatollah Ebrahim Raisi (2nd right) pays respects to the body of slain scientist Mohsen Fakhrizadeh among his family, in the capital Tehran on Saturday. Photo: AFP

Iran's president on Saturday accused arch-foe Israel of acting as a US "mercenary" and seeking to create chaos, vowing Tehran would avenge the assassination of a top Iranian nuclear scientist.

The Islamic republic's supreme leader Ayatollah Ali Khamenei called for the perpetrators to be punished, while President Hassan Rouhani stressed the country would seek its revenge in "due time" and not be rushed into a "trap."

Scientist Mohsen Fakhrizadeh, dubbed by Israel as the "father" of Iran's nuclear program, died on Friday after being seriously wounded when assailants targeted his car and engaged in a gunfight with his bodyguards outside Tehran, according to Iran's defense ministry.

The assassination comes less than two months before US President-elect Joe Biden is due to take office, after a tumultuous four years of hawkish foreign policy in the Middle East under President Donald Trump.

"They are thinking of creating chaos, but they should know that we have read their hands and they will not succeed," Rouhani said.

He pinned the blame for the killing on "the wicked hands of the global arrogance, with the usurper Zionist regime as the mercenary."

Iran generally uses the term "global arrogance" to refer to the US.

Students vented their anger by calling for revenge and burning US and Israeli flags outside Iran's foreign ministry in Tehran, as well as pictures of Trump and Biden.

Trump unilaterally withdrew in 2018 from a multilateral nuclear deal with the Islamic republic, which sought to contain its atomic ambitions, and has reimposed crippling sanctions. But Biden has signaled his administration may be prepared to rejoin the accord.

The US slapped sanctions on Fakhrizadeh in 2008 for "activities and transactions that contributed to the development of Iran's nuclear program," and Israeli Prime Minister Benjamin Netanyahu once described him as the father of Iran's nuclear weapons program.

Iran has repeatedly denied seeking to develop nuclear weapons.

The New York Times said an American official and two other intelligence officials confirmed Israel was behind the attack, without giving further details.

Former CIA director John Brennan warned the assassination risked sparking a wider conflagration in the Middle East.

The UN called for restraint.

"We urge restraint and the need to avoid any actions that could lead to an escalation of tensions in the region," a spokesman said. 

AFP