Iran 'halted enrichment temporarily' says UN watchdog
Iran temporarily stopped enriching uranium earlier in November, according to the UN nuclear watchdog.
The International Atomic Energy Agency gave no reason for the temporary halt in the enrichment of low-grade uranium.
But there was speculation that a complex computer worm which infected the personal computers of staff at the country's first nuclear power station, at Bushehr, might be the reason.
Iran on Tuesday denied that the Stuxnet worm had caused any damage.
The West fears Iran's ultimate goal is to build nuclear weapons. Iran says its programme is aimed solely at peaceful energy use.
In a report leaked to several news agencies, the IAEA said that none of the centrifuge units at Iran's Natanz plant were being fed for enrichment to lower-levels when inspectors visited the site on 16 November.
On both earlier and subsequent visits more than 4,800 such centrifuges were being fed with nuclear material.
It was not clear whether the technical problems suffered at the plant, which are reported to have included power fluctuations, were due to the computer virus.
One senior diplomat quoted anonymously by Reuters news agency said that Iran was using an old centrifuge model which has been dogged by breakdowns for years.
"I don't think you can necessarily blame Stuxnet entirely. There could be some other issues but clearly they have been having some real problems," the senior diplomat told Reuters.
Cyber experts say the worm, which Iran said in September had attacked its computers, has been configured to damage centrifuges and is capable of seizing control of industrial plants.
Some Western experts have said its complexity suggests it could only have been created by a "nation state". Senior Iranian officials have said that the virus is evidence that an "electronic war" has been launched against the country.