All Eyes on Israel After Second Iranian Blast By Sheera Frenkel, Jerusalem

The second blast in as many weeks at an atomic or missile facility has sparked Iranian denials and claims of accidents, but a new phase in efforts to destroy its nuclear ambitions is said to be under way.

"Instead of overt action you have covert action. This is the new battlefront — this is a new kind of war," an Israeli defence official said.

The Israeli Defence Minister, in a radio interview yesterday, did little to dampen speculation that it had a role in the blast at Isfahan, located in central Iran, and an explosion at a missile base west of Tehran.

Ehud Barak, acknowledging that Israel stood to benefit most from disruption to the nuclear program, said: "We are not happy to see the Iranians move ahead on this (program), so any delay, be it divine intervention or otherwise, is welcome."

More than 20 members of the Revolutionary Guards died in the explosion at the missile base two weeks ago, including General Hassan Moghaddam, described as the architect of Iran's missile program.

The facilities in Isfahan are involved in converting uranium yellowcake ore into uranium hexafluoride, part of the process of enriching it to fuel or weapons-grade material. A US official yesterday dismissed Iranian claims that the Isfahan explosion took place at a nearby site and not at the nuclear facility, but said it was unclear how much damage had been done.

Half a dozen other incidents of mysterious explosions and accidental deaths have been reported in the past two years. They range from a blast at a base housing a medium-range Shahab-3 missile near the western city of Khorramabad in October last year to the killing of Dariush Rezaei, a nuclear scientist, in Tehran in July. The deployment of Stuxnet last year, a computer virus that wreaked havoc on uranium-enrichment centrifuges, defined modern cyber-warfare.

Covert action suits Israel, hampering the nuclear program without provoking a direct confrontation, sources said. One Western intelligence official said the incidents were "perfect for Israel".

"You have Iran's nuclear weapons program slowed down. On the other hand, you don't have to take responsibility for doing anything, and Iran will continue to deny them and call them accidents."

He said this "served both parties for the time being" but that it could "only continue for so long".

When and how Israel could launch a full attack is still being debated by its officials. They have said that they would seek the support of the West, though US and British officials have said that they do not know whether Israel would give them warning.