The massive blast at an Iranian nuclear plant earlier this week remains shrouded in mystery, but it cleared up one thing, according to those who track the Islamic Republic: The nuclear weapons program Tehran has long denied is real.

The massive blast Sunday night rocked buildings more than 10 miles away, and before-and-after satellite images published by Israel Defense showed startling destruction at a facility Iran has repeatedly barred international inspectors from entering.

“[The] images indicate that a complete section of structures was simply eliminated by an unexplained explosion,” Israel Defense analyst Ronen Solomon said. “The explosion wiped several testing units off the face of the earth while inflicting collateral damage on adjacent buildings.”

Iran, which initially denied an explosion took place, was forced a day later to own up to a blast, via the IRNA official Iranian news agency. The report said two people had been killed as a result of a fire at the site. The true casualty figure may never be known.

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Israel has long insisted that Iran’s charm offensive, successful in easing western sanctions, is a ruse to buy time while it pursues nuclear weapons.

“Don’t be fooled by Iran’s manipulative charm offensive,” Israeli Prime Minister Benjamin Netanyahu warned the UN General Assembly in New York on Sept. 29. “It’s designed for one purpose and for one purpose only: to lift the sanctions and remove the obstacles to Iran’s path to the bomb.

“Once Iran produces atomic bombs,” Netanyahu added, “all the charms and all the smiles will suddenly disappear. They’ll just vanish. And it’s then that the ayatollahs will show their true face and unleash their aggressive fanaticism on the entire world.”

As in past cases when things explode or scientists are killed in Iran, speculation centers on Israeli intelligence agencies, who, just as predictably, do not comment. Both misplaced blame and proper credit serve the purpose of burnishing their reputation within enemy and terrorist regimes. There are other possibilities, including that it was an accident or that Iranian dissident groups or western intelligence agencies played a role.

“If someone did succeed in infiltrating the Parchin site with explosives and causing the huge explosion which took place there, we are talking about an exceptional achievement,” regional terror analyst Ronen Bergman suggested in Wednesday’s Ynet.com.

Parchin, a site to which international inspectors have repeatedly been denied access since 2007 – a fact that many opponents of the P5+1 talks have long insisted in itself makes a mockery of the so-called negotiation process – is rumored to be the location of the development of the key warhead components required for making a nuclear bomb.

“Western officials suspect that at the heart of this secret development is the weapon group developing the nuclear lens mechanism,” Bergman said. “It's a complex system of timers and explosives assembled around the core of the bomb, which explode in a way that "pushes" the enriched uranium sphere inwards and starts the chain reaction needed for an atomic explosion. If the smoking gun for the existence of the weapon group is found, it will serve as decisive evidence that Iran has been lying and that there is no point in negotiating with it.”

The assassination of a series of Iranian nuclear scientists inside Iran in recent years as the result of bombs planted on, or next to their vehicles by mysterious motorcycle-riding hitmen, together with the vicious Stuxnet computer virus that hit Iran’s key Natanz nuclear facility in 2010, has allegedly put the brakes on the Islamic Republic’s nuclear project.

According to Amnesty International, thousands of dissidents languish in Iranian jails, (including a significant number of journalists). Iran is second only to China in the number of executions it carries out each year, often following only a token trial.

 Regime support is also indicated in the September 2013 massacre of at least 52 Iranians in neighbouring Iraq at the Camp Ashraf refugee camp that had been designated a safe haven for Iranian activists, many of whom had opposed the direction of their nation’s nuclear ambitions. U.S. officials were reportedly furious at Iran’s Revolutionary Guard praising the attack, while Foreign Policy magazine reported that, “U.S. intelligence officials believe that Iranian commandos took part [in the attack].”

Paul Alster is an Israel-based journalist. Follow him on Twitter @paul_alster and visit his website: www.paulalster.com.