General Ali Resa Asgari, 63, was missing since February 7 after arriving in Istanbul on a flight from Syria.

Asgari was Iran's deputy defence minister for eight years till 2005. Before that, he was a prominent general in Iran's Revolutionary Guards.

Debkafile, a leading Web site on Middle East affairs, first reported the disappearance on March 2, and also identified Asgari as the officer in charge of Iranian undercover operations in central Iraq.

External link: Did he leave or was he kidnapped?

On March 8, several reports in the Western media confirmed that Asgari had fled to the West, the first senior Iran official to defect since the revolution 27 years ago.

Reports said Asgari will be crucial to the West to get reliable information on how Iran runs its operations in Lebanon.

Iran has been accused of using Hezbollah to launch suicide bomb attacks against Western and Israeli targets in southern Lebanon.

British newspaper The Times reported that Asgari will also help Hezbollah's adversaries to have accurate estimates of stockpiles and tactics of the group.

In 2006, Israel and Hezbollah were engaged in a 33-day war after the group seized two Israeli soldiers. Hezbollah leader Sheikh Hassan Nasrallah had then said: 'Israel doesn't know our capabilities on every level. The Zionist enemy has not succeeded in infiltrating our group.' General Asgari could lift that veil of secrecy, the Times report said.

'It means for the first time, Hezbollah's adversaries may have accurate estimates of stockpiles, weapons types, even perhaps placement and tactics,' the report quoted Nicholas Noe, the author of a forthcoming book on Hezbollah. 'This is crucial because the limits and placement of Hezbollah's weaponry has been a major problem.'

Iranian officials have played down Asgari's importance, saying he has been out of the loop for four or five years.

But his defection could cause a serious blow to Iran, which has meanwhile notified Interpol and raised fears that Asgari might have been kidnapped.