The assassination of an Iranian nuclear scientist sparked deep fury in Tehran on Thursday against prime suspect Israel and against the United States, which said it had nothing to do with the murder.

Some hardline newspapers even called for retaliatory action, with one, Keyhan, saying in an editorial that "assassinations of Israeli officials and military are achievable."

The government's reaction was just as angry, though more measured.

In a letter demanding strong UN Security Council condemnation, it said it had evidence unnamed "foreign quarters" were behind Wednesday's killing of scientist Mostafa Ahmadi Roshan.

The 32-year-old deputy director of Iran's Natanz uranium enrichment facility died when two riders on a motorbike drove by his car trapped in Tehran's rush-hour and slapped onto it a magnetic bomb that directed a deadly blast inside the vehicle.

The explosion also killed Ahmadi Roshan's driver/bodyguard and wounded a third occupant of the Peugeot 405.

The attack was similar to four others in Tehran over the past two years. Three scientists died, at least two of whom also worked on Iran's controversial nuclear programme.

Another, who now heads the country's atomic energy organisation, escaped just in time.

Ahmadi Roshan was to be buried on Friday, after traditional weekly Muslim prayers.

The latest attack dominated Iran's media on Thursday, with many outlets criticising what they said was the silence of the West over the killings. More conservative titles urged tit-for-tat covert action against Israel.

"The only way to finish with the enemy's futile actions is retaliation for the assassination of Iran's scientist," said the newspaper Resalat.

"It is legal under international law to retaliate for the killing of the nuclear scientist," the daily Keyhan said. "The Islamic republic has gathered much experience in 32 years, thus assassinations of Israeli officials and military members are achievable."

Protests called for Thursday outside the French, German and British embassies were cancelled for lack of authorisation, Fars news agency reported, adding they would be now be held after Friday's funeral.

The British embassy has been closed since protesters angry at Western sanctions ransacked it in November. The United States and Israel do not have diplomatic ties with Iran. The French mission is operating on reduced staff.

On Wednesday, Vice President Mohammad Reza Rahimi, the foreign ministry, lawmakers and other officials said Israel and the United States were behind the car-bomb attack.

US President Barack Obama and Israeli Prime Minister Benjamin Netanyahu spoke by phone on Thursday.

The White House said in a statement they "discussed recent Iran-related developments, including the international community's efforts to hold Iran accountable for its failures to meet its international obligations."

Israel has largely remained silent, although military spokesman Brigadier General Yoav Mordechai said on his official Facebook page that, while he was unaware who carried out the killing, "I am definitely not shedding a tear."

Israeli media highlighted comments by the chief of staff, Lieutenant General Benny Gantz, saying the day before the attack that 2012 would be a critical year for Iran, in part because of "things which happen to them (the Iranians) in an unnatural way."

Secretary of State Hillary Clinton "categorically" denied US involvement in the bombing.

Iran's powerful Revolutionary Guards, however, were adamant that "the terrorist actions against our nuclear scientists and experts is a US-Zionist plot."

The Guards have previously warned they could strike at enemy targets far beyond Iran's borders should their country be threatened.

Russian Security Council secretary Nikolai Patrushev warned in an interview published by the daily Kommersant that military escalation over Iran was likely and that "Israel is pushing the Americans towards it."

"There is a real danger of a US military strike on Iran," he said.

US-Iran tensions are already fraught following an Iranian court's death sentence this week on an American-Iranian former Marine it found guilty of spying for the CIA, and Iran's capture last month of what it said was a CIA drone.

The Guards have announced new naval manoeuvres in the Strait of Hormuz in the Gulf within the next few weeks, underlining Iran's threat to close the narrow channel -- a choke point for a fifth of the world's oil -- if an attack or heavy sanctions are imposed.

Washington has responded by warning that closing the strait would be a "red line" Iran should not cross. It has sent a second aircraft carrier to waters just outside the Gulf, and a third was on its way.

At the same time, the United States and other Western powers are ratcheting up sanctions on Iran to halt Tehran's nuclear programme they believe masks a drive to research development of atomic weapons.

Iran's parliament speaker Ali Larijani was holding talks with Turkish leaders on Thursday about the nuclear programme, which the Islamic republic insists is exclusively for peaceful purposes.

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