The report comes after the complex worm Stuxnet infected staff computers at Iran's first nuclear power station at Bushehr.

No details of the arrests were given.

Iranian Intelligence Minister Heidar Moslehi was cited by Press TV as saying his ministry was capable of countering any threats.

"We are always facing destructive activities by these [espionage] services, and, of course, we have arrested a number of nuclear spies to block the enemy's destructive moves," Mr Moslehi said.

But he did not say how many people were detained, or specify whether the cyber attack referred to the Stuxnet virus.

While the worm also affected computers India, Indonesia and the US, it has spread the most in Iran.

Reports suggest that the Stuxnet virus mutated in Iran and infected 30,000 computers.

It is believed to be the first worm designed to target major infrastructure facilities.

Iran's Russian-built Bushehr plant will start generating power in January, two months later than planned, but officials have said the delay was not due to the virus.

Some experts have said the virus was designed to target Tehran's nuclear programme, with some saying the complexity could only have been created by a state.

Iran has been subject to four rounds of UN sanctions because of its uranium enrichment programme, which is separate from Bushehr.

The West fears Tehran wants to build a nuclear weapon, but Iran insists its plans are for peaceful energy production.