An Iranian military commander has accused German engineering company Siemens of helping the United States and Israel launch a cyber attack on its nuclear facilities, Kayhan daily reported on Sunday.

Gholamreza Jalali, head of Iran's civilian defense, said the Stuxnet virus aimed at Iran's atomic program was the work of its two biggest foes and that the German company must take some of the blame.

Open gallery view The reactor building of the Bushehr nuclear power plant is seen, just outside the southern city of Bushehr, Iran. Credit: AP

Siemens declined to comment.

"The investigations show the source of the Stuxnet virus originated in America and the Zionist regime," Jalali was quoted as saying.

Jalali said Iran should hold Siemens responsible for the fact that its control systems used to operate complicated factory machinery, known as Supervisory Control and Data Acquisition (SCADA), had been hit by the worm.

"Our executive officials should legally follow up the case of Siemens SCADA software which prepared the ground for the Stuxnet virus," he said.

"The Siemens company must be held accountable and explain how and why it provided the enemies with the information about the codes of SCADA software and paved the way for a cyber attack against us," he said.

Some foreign experts have described Stuxnet as a "guided cyber missile" aimed at Iran's atomic program.

Unlike other Iranian officials who have played down the impact of Stuxnet, Jalali said it could have posed a major risk had it not been discovered and dealt with before any major damage was done.

"This was a hostile act against us which could have brought major human and material damages had it not been encountered promptly."

Iran has given few details of the impact of the virus. It said in September that staff computers at the Russian-built Bushehr nuclear power station had been hit but that the plant itself was unharmed.

Bushehr, Iran's first nuclear power station, is still not operational, having missed several start-up deadlines, prompting speculation that it too had been hit by Stuxnet, something Iran denies.

Russia's ambassador to NATO said in January the virus had hit the computer system at Bushehr, posing the risk of a nuclear disaster on the scale of the 1986 Chernobyl incident in Ukraine, then part of the Soviet Union.

Some defense analysts say the main target was more likely to be Iran's uranium enrichment, the process which creates fuel for nuclear power plants or provides material for bombs if processed much further. Western powers accuse Iran, a major oil producer, of seeking to develop nuclear weapons capability, something Tehran denies.

U.S.-based think-tank, the Institute for Science and International Security (ISIS), said that in late 2009 or early 2010 about 1,000 centrifuges out of the 9,000 centrifuges used at Iran's Natanz enrichment plant, had been knocked out by the virus, not enough to seriously harm its operations.