Jerusalem, May 29 - An unprecedented "cyber espionage worm" considered the most sophisticated spyware virus yet unleashed, attributed to a "state player", has hit Iran and other Middle Eastern countries with the possible goal of foiling Tehran's nuclear ambitions.

Security experts discovered the new data-stealing virus dubbed Flame which they say has lurked inside thousands of computers across the Middle East for as long as five years as part of a sophisticated cyber warfare campaign.

Russia-based Internet security company Kaspersky Lab that uncovered the virus 'Flame' said it is designed to collect and delete sensitive information.

Kaspersky, one of the world's biggest producers of anti- virus softwares, said the bug had infected computers in Iran, the West Bank, Sudan, Syria, Lebanon, Saudi Arabia and Egypt.

Flame is "actively being used as a cyber weapon attacking entities in several countries," Kaspersky said in a statement, describing its purpose as "cyber espionage".

"The complexity and functionality of the newly discovered malicious programme exceed those of all other cyber menaces known to date," the statement said.

The Internet security company also said that Flame contained a specific element that was used in the Stuxnet worm and which had not been seen in any other malware since.

On its blog, Kaspersky called Flame a "sophisticated attack toolkit," adding that it was much more complex than Duqu, the vehicle used to deliver Stuxnet.

The Stuxnet bug, discovered in June 2010, targeted primarily Iranian computers. Iran admitted that the worm had damaged centrifuges operating at an uranium enrichment facility at Nantaz. PTI