A large explosion that killed a senior Iranian Revolutionary Guard commander near Tehran last Saturday has been attributed by various intelligence sources to Mossad. The blast is the latest in a series of unattributed attacks against Iran's nuclear programme.

Meanwhile, Israeli diplomats have expressed concern over the international response to last week's report by the International Atomic Energy Agency, which detailed the steps Iran has been taking towards gaining a military nuclear capability.

Germany, France and Turkey have announced their opposition to a potential attack by Israel on Iran's nuclear infrastructure, while the Obama administration has refrained from voicing support.

Prime Minister Benjamin Netanyahu, who ordered his ministers not to make public statements about the IAEA report, said last Sunday that "Iran is closer than it seems to a bomb" and called upon "every responsible government in the world to draw the necessary conclusions".

General Hassan Moghaddam, who was killed along with at least 16 other members of the Revolutionary Guards in the huge explosion at a missile base near Tehran, was a central figure in the Iranian missile programme. He had been working on the development of the long-range Shahab-3 missile, capable of hitting targets at a range of over 1,200 miles.

While the Iranian authorities insisted that the explosion was caused by an accident during the transport of ammunition at an arms depot, Western and Israeli intelligence sources suggested that the base was actually being used for the storage of Shahab-3 missiles. They also ventured that Moghaddam had been targeted by Mossad, perhaps with the aid of members of the Iranian opposition group Mujahedin el-Khalk.

As in recent assassinations of major figures in Iran's weapons programmes, such as senior nuclear scientists, official Israeli sources refused to comment.

Another possible sabotage of Iran's nuclear programme was acknowledged this week by its civil defence authorities who reported that they had detected a new computer virus, "Duqu", that had attacked some key military computer systems. The Iranians claimed that the virus had not damaged its computers. Duqu is apparently a "worm" programme that takes advantage of weaknesses in Microsoft's Windows operating system.

The latest cyber-attack on Iran is reminiscent of the Stuxnet worm that debilitated the computers operating Iranian uranium-enrichment centrifuges last year. According to reports, Stuxnet put around 1,000 centrifuges out of commission for months.

No country or organisation took responsibility for Stuxnet, but computer experts argued that such a complex code could have been written only by a country with extensive software development resources such as the US or Israel.

Stuxnet contained various codes associated with the story of Purim, and a report on the cyber-attack featured briefly in an IDF film produced to mark the departure of the previous chief of staff, Gabi Ashkenazi.

Last week's IAEA report has played a significant part in the American presidential election debates.

Republican candidates have been criticising President Barack Obama for being "soft" on Iran. Republican frontrunner Mitt Romney said last weekend: "If we re-elect Barack Obama, Iran will have a nuclear weapon. If you elect me as the next president, they will not have a nuclear weapon."

Mr Romney suggested the US co-operate "with the insurgents in the country to encourage regime change", but stressed that if "there's nothing else we can do besides take military action, then of course we take military action."