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.

Reports of a significant and damaging explosion at the underground Fordow bunker, near the religious city of Qom, emerged on Friday, though there was no verification of its authenticity.

Tehran has accused Israel and the United States of being behind cyber attacks 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 Fordow is Western propaganda ahead of nuclear negotiations to influence their process and outcome," state news agency IRNA 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.

The plant at Fordow in late 2011 began producing uranium enriched to 20 percent fissile purity, compared with the 3.5 percent 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 towards developing a nuclear weapons capability.

Iran maintains 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 location.