Ali Reza Asgari, a retired general who served in Iran's Revolutionary Guard, disappeared while on a private trip to Turkey in December, 2006. In March of this year, a former German Defence Ministry official said Mr Asgari had defected and was providing information to the West on Iran's nuclear program. Iranian officials and Mr Asgari's family have claimed that he was abducted.
One of yesterday's web reports, on a site called Alef, said German and British intelligence services assisted Israeli agents in abducting Mr Asgari and taking him to Israel.
The site, www.alef.ir, is close to a conservative Iranian law-maker.
"On the basis of a two-year investigation carried out by concerned bodies, Asgari was abducted by foreign intelligence services and is being held in a Zionist prison," the site reported, apparently referring to an Iranian intelligence probe into the matter.
Israel's Foreign Ministry refused to comment.
Hans Ruehle, a former chief of the planning staff of the German Defence Ministry, wrote in a Swiss newspaper in March that Mr Asgari told the West that Iran was financing North Korean steps to transform Syria into a nuclear weapons power, leading to an Israeli air-strike that targeted a site in Syria on September 6, 2007.
The US claims the site was a nearly finished nuclear reactor, but Syria denies that and says the facility was an unused military installation. Mr Ruehle said Mr Asgari, who was instrumental in establishing the Hezbollah militant group in Lebanon, "changed sides" and provided information to the West on Iran's own nuclear program.
The US and its European allies, as well as Israel, suspect Iran is intent on using a civilian nuclear program as a cover for developing nuclear weapons. Iranian officials have said Mr Asgari was not linked to Iran's nuclear program, but Western media reports have said he has co-operated with US intelligence and is considered a "high value" defector. Mr Asgari arrived in Turkey on December 7, 2006, and disappeared on December 9.