A defiant Iran admitted Monday that its atomic programme may have come under cyber-attack as one of its top nuclear scientists was killed by a bomb attached to his car in the capital and another was wounded by a similar device.

President Mahmoud Ahmadinejad blamed the attacks against the two senior scientists in Iran's controversial nuclear programme on Israel and Western powers led by the United States which accuse Iran of seeking to make atomic weapons.

Majid Shahriari was killed and his colleague Fereydoon Abbasi Davani was injured when men on motorcycles attached bombs to their cars in different parts of the capital as they made their way to work, police said.

Three others including the men's wives and a driver were also injured.

"One can undoubtedly see the hands of the Zionist regime and Western governments in the assassination which unfortunately took place," Ahmadinejad told a news conference.

Interior Minister Mostafa Mohammad Najjar blamed the Israeli spy agency Mossad and the CIA.

Israel's foreign ministry declined to comment on the reports.

Shahriari was "in charge of one of the great projects" at Iran's Atomic Energy Agency, nuclear chief, Ali Akbar Salehi told the state news agency IRNA.

He was also a member of the so-called SESAME project on nuclear cooperation in the Middle East and conservative website Rajanews said he headed a "project that sought to achieve the technology to design nuclear reactor core."

The other scientist, Abbasi Davani, was targeted by UN Security Council sanctions under Resolution 1747 adopted in March 2007. He was identified as a senior defence ministry and armed forces logistics scientist.

In January, Masoud Ali Mohammadi, another Iranian nuclear scientist involved with the SESAME project, was killed in a bomb attack which Tehran blamed on "mercenaries" in the pay of Israel and the United States.

Iran is under four sets of UN sanctions over its refusal to suspend uranium enrichment, the sensitive process which can be used to make nuclear fuel or, in highly extended form, the fissile core of an atom bomb.

Western governments suspect Iran's nuclear programme masks a drive for an atomic weapons capability, an ambition Tehran has steadfastly denied.

The Islamic republic is likely to resume stalled negotiations with world powers on its controversial nuclear programme in Geneva on December 5.

But a defiant Ahmadinejad said on Monday that Iran's "right to enrich uranium and produce (nuclear) fuel... is non-negotiable."

Despite previous denials by other Iranian officials, Ahmadinejad also admitted that "several" uranium enrichment centrifuges were damaged by malware amid speculation Iran's nuclear activities had come under cyber-attack.

"They were able to create problems on a limited basis for some of our centrifuges by software installed in electronic equipment," Ahmadinejad said.

"Our specialists stopped that and they will not be able to do it again," he added without elaborating on the software thought to have been used.

The Vienna-based International Atomic Energy Agency, the UN nuclear watchdog, said in its latest report last week that a one-day outage had hit Iran's Natanz uranium enrichment plant earlier this month.

The United States and Israel -- the sole if undeclared nuclear power in the Middle East -- have never ruled out a military strike to curb Iran's atomic drive.

And on Sunday the chairman of the US joint chiefs of staff, Admiral Mike Mullen, said the United States was weighing military options in the face of Tehran's announcement it had an atomic power plant up and running.

As Iran comes under mounting pressure, whistleblower website WikiLeaks released diplomatic cables on Sunday revealing that Saudi Arabia's king "repeatedly" urged Washington to take military action against Iran.

Ahmadinejad dismissed the documents as "worthless" and "mischief," insisting Tehran's relations with its Arab neighbours would not be affected.

But US Secretary of State Hillary Clinton said their content underlined the world's concern about Iran's nuclear programme.

"Any of the comments that are being reported on, allegedly from the cables confirm the fact that Iran poses a very serious threat in the eyes of many of her neighbours and a serious concern far beyond her region," Clinton told a press briefing.