Iran has accused the German engineering firm Siemens of helping Israel and the US launch a computer worm designed to sabotage its nuclear facilities.

A senior Iranian military commander said that the company facilitated the Stuxnet worm cyber-attack against Iran by providing Washington and Jerusalem with information about a Siemens-designed control system, SCADA, used in Iran's nuclear sites.

"Our executive officials should legally follow up the case of Siemens SCADA software which prepared the ground for the Stuxnet worm," Gholamreza Jalali, Iran's civil defence chief was quoted by the IRNA state news agency as saying.

"Siemens should explain why and how it provided the enemies with the information about the codes of the SCADA software and prepared the ground for a cyber attack against us," he added.

Iran initially played down the impact of the malware after its first appeared in July 2010, but in November President Mahmoud Ahmadinejad admitted that the nuclear programme had been affected . However he said that the issues had been resolved without any serious damage.

According to Jalali, an internal investigation revealed that the worm had been disseminated from sources in the US and Israel.

"It was a hostile action which could have inflicted serious damage on the country if it had not been dealt with in a timely manner," he said. Last year, Iran assigned an expert group to combat the computer worm.

Both the US and Israel, which are reported to be conducting covert operations against Iran's nuclear programme, have not denied computer experts' claims that they were behind the development of the Stuxnet worm.

The New York Times reported in January that intelligence services in both countries collaborated in a joint project to develop a malware which targeted the industrial management software that Iran uses to run its centrifuges.

In March, Ralph Langner, a leading security expert told a conference in California that in his opinion the Israeli intelligence service, the Mossad, was involved but that "there is only one leading source, and that is the United States."

Siemens did not respond to the Guardian's request on Sunday for an interview over Iran's allegations of its involvement in developing the malware.

Last year, apart from the Stuxnet worm, Iran's nuclear programme suffered from the assassinations of three of its scientists in operations that some analysts asserted might be a part of the convert war against Iran.

Siemens was also caught in another row involving Iran when an imprisoned Iranian activist filed a suit against the company and its joint venture with Nokia, NSN, in August 2010 over allegations that they have provided Iran's state-run telecommunications company with a monitoring system that it has used to spy on its opposition.