The malicious Stuxnet computer worm has hit 30,000 industrial computers in Iran, officials said today, but denied the Islamic republic's first nuclear plant at Bushehr was among those infected.

So far, Stuxnet has infected about 30,000 IP addresses in Iran, Mahmoud Liayi, head of the information technology council at the ministry of industries, was quoted as saying by the government-run newspaper Iran Daily.

Stuxnet, which was publicly identified in June, was tailored for Siemens supervisory control and data acquisition, or SCADA, systems commonly used to manage water supplies, oil rigs, power plants and other industrial facilities.

The worm is able to recognise a specific facility's control network and then destroy it, according to German computer security researcher Ralph Langner, who has been analysing the malicious software.

Langner said he suspected Stuxnet was targetting Bushehr nuclear power plant, where unspecified problems have been blamed for delays in getting the facility fully operational.

Siemens said its software has not been installed at the plant, and an Iranian official denied the malware may have infected nuclear facilities.

"This virus has not caused any damage to the main systems of the Bushehr power plant," Bushehr project manager Mahmoud Jafari said on Iran's Arabic-language Al-Alam television network.

"All computer programmes in the plant are working normally and have not crashed due to Stuxnet," said Jafari, adding there was no problem with the plant's fuel supply.

The official IRNA news agency meanwhile quoted him as saying the worm had infected some "personal computers of the plant's personnel."

And he told Fars news agency that so far, five versions of the malware had been detected in Iran.