Newsmaker

Iranian investigators have determined the cause of a fire at the Natanz nuclear plant, a spokesman for Iran's top security body said on Friday, while declining to immediately release details of the findings over "security reasons".

The National Security Council's statement came as Gholamreza Jalali, the head of Iran's civilian defence, told state television that Tehran would retaliate against any country that carries out cyberattacks on its nuclear sites.

Reuters News Agency, citing three Iranian officials, said the fire at Natanz, which occurred early on Thursday, was caused by cyber sabotage.

But Reuters said the officials did not offer evidence to back the claim.

The Natanz uranium-enrichment site, much of which is underground, is one of several Iranian facilities monitored by inspectors of the International Atomic Energy Agency (IAEA), the United Nations nuclear watchdog.

Iran's Atomic Energy Organisation initially reported an "incident" had occurred early on Thursday at Natanz, located in the desert in the central province of Isfahan. It later published a photo of a one-storey brick building with its roof and walls partly burned.

A door hanging off its hinges suggested there had been an explosion inside the building.

The IAEA said none of its inspectors was at Natanz at the time of the fire and "that the location where the incident occurred does not contain nuclear materials".
Keyvan Khosravi, spokesman for the National Security Council, told IRNA news agency late on Friday that experts have "determined the main cause of the incident" but it "will be declared in due course for security reasons".

The mystery around the incident deepened after BBC reported that an unknown group called the "Cheetah's of the Homeland" claimed responsibility for the attack in a statement sent to the network's Persian service journalists before news of the fire became public.

A video claimed the group included "soldiers from the heart of regime's security organisations" who wanted to stop Iran from acquiring a nuclear weapon. Iran long has maintained its atomic programme is for peaceful purposes.
At the same time, Iranian media has cast suspicion on the US and Israel for the incident.

In an article issued on Thursday, IRNA addressed what it called the possibility of sabotage although it stopped short of accusing either US or Israel directly.

"So far, Iran has tried to prevent intensifying crises and the formation of unpredictable conditions and situations," IRNA said. "But the crossing of red lines of the Islamic Republic of Iran by hostile countries, especially the Zionist regime and the US, means that strategy... should be revised."

In 2010, the Stuxnet computer virus, which is widely believed to have been developed by the US and Israel, was discovered after it was used to attack the Natanz facility.

Later on Thursday, Jalali told state TV that "if it is proven that our country has been targeted by a cyberattack, we will respond".