Iran has denied media reports of a major explosion at one of its uranium enrichment sites, describing them as "Western propaganda" designed to influence upcoming nuclear negotiations.
Reuters has been unable to verify reports since Friday of an explosion at the underground Fordo bunker, near the holy city of Qom, that some Israeli and Western media have said caused significant damage.
The London Times reported on Monday that Israeli officials confirmed that the blast happened last week.
Vice Premier Strategic Affairs Minister Moshe Ya'alon (Likud) played down any Israeli involvement.
"I read about it in the paper," Ya'alon told Army Radio early Monday morning. "We've heard about worms, viruses and explosions in the past. All of these efforts delay Iran's nuclear program. If such disturbances hadn't hit Iran in the last number of years, Tehran would have developed a military nuclear program a long time ago."
Tehran has accused Israel and the United States of being behind cyberattacks and the assassination of its nuclear scientists, aiming to sabotage a nuclear program which the West suspects hides an attempt to develop nuclear weapons.
"The false news of an explosion at Fordo is Western propaganda ahead of nuclear negotiations to influence their process and outcome," the government-run Islamic Republic News Agency quoted the deputy head of Iran's Atomic Energy Organization, Saeed Shamseddin Bar Broudi, as saying late on Sunday.
The IRNA report also quoted the head of parliament's national security and foreign affairs committee, Alaeddin Boroujerdi, strongly denying there had been an explosion.
In late 2011, the plant at Fordo began producing uranium enriched to 20 percent fissile purity, compared with the 3.5% level needed for nuclear energy plants, and has been operating 700 centrifuges there since January this year, according to Western diplomats.
Western governments are concerned that high-grade enrichment is a significant step toward developing a nuclear weapons capability.
Iran maintains that its nuclear activities are entirely peaceful and that it began producing high-enriched uranium that it was no longer able to obtain from abroad for medical use.
The two sides are set to resume negotiations in coming weeks but the talks have been beset by delays and wrangling over dates and locations.