A computer virus that experts said may have been created by a state did not affect Iran's nuclear plant or government systems, but did hit computers of staff at the plant and Internet providers, officials said on Sunday.
A senior official at US technology company Symantec told Reuters on Friday that 60 per cent of the computers worldwide infected by the so-called Stuxnet worm were in Iran, prompting speculation that the nuclear power plant may have been targeted in an attempt at sabotage or espionage.
Some Western cyber security companies suggested the attack could only have been conducted "with nation-state support", indicating industrial plants in the Islamic state were the target.
The head of the Bushehr nuclear power plant said the virus had only affected personal computers of staff.
"A team is inspecting several computers to remove the malware ... major systems of the plant have not been damaged," Mahmoud Jafari told the official Irna news agency.
Russia was fiercely criticised by the West for involvement in completing the long-mothballed plant. Moscow says the plant is purely civilian.
Iran's Telecommunications Minister Reza Taqipour said the worm had not been able to "penetrate or cause serious damage to government systems", the state-run newspaper Iran Daily reported.
Authorities said Iran had identified some 30,000 Internet providers infected by the Stuxnet worm, blaming Iran's "foreign enemies for creating the virus".
Diplomats and security sources say Western governments and Israel view sabotage as one way of slowing Iran's nuclear work, which the West fears is aimed at building bombs. Tehran says it needs nuclear technology to generate electricity.
The malware attacks software programs that run Supervisory Control and Data Acquisition, or SCADA, systems. Such systems are used to monitor automated plants -- from food and chemical facilities to power generators.
"The Stuxnet spy worm has been created in line with the West's electronic warfare against Iran," the newspaper quoted Mahmoud Liayi, secretary of the Information Technology Council of the Industries Ministry, as saying.
Israel, which is assumed to have the Middle East's only atomic arsenal, has hinted it could attack Iran's nuclear facilities if international diplomacy fails to curb the country's programme.