An arms deal gone bad? A bungled attempt to obtain intelligence? Or internal rivalries within the Russian security establishment?

Whatever the case, the arrest of Colonel Vadim Leiderman, Israel's military attache to Russia, in Moscow two and a half weeks ago was a rare occurrence in the normally stable relationship between the two countries.

Col. Leiderman, a senior air-force engineer, was arrested by the FSB, successors to the KGB, despite his diplomatic immunity, and questioned in what was described as "humiliating conditions".

Following his release, he was put on an El Al plane back to Israel. Upon arrival, he was taken for questioning by the Shin Bet.

"As we did not know any intelligence work he was supposed to be involved in, we had to make sure that he wasn't embarking on any private spying initiative, or worse, operating on behalf of another country. He was questioned for a week and ultimately cleared."

His colleagues were surprised that Col. Leiderman's name even came up. "Nothing in his character or his previous career has any connection to spying," said a former Israel Air Force general, who had worked closely with him. "He is an engineer, not James Bond."

Born in the former Soviet Union and an emigree to Israel as a child, Mr Leiderman, 48, served in the Air Force's Materiel Command as an expert on airframes.

His last position in the Air Force was in command of the planning and budgets department of the Materiel Command. The attaché job in Moscow was supposed to be his last posting before retirement this summer and, for the past three years, he has been the point-man in Israel's complex security relationship with Russia.

Although the two countries exchange intelligence, and Israel recently sold unmanned airborne vehicles to Russia for $400m, the Jewish state has serious concerns regarding Russia's sale of advanced missiles to Syria and Iran.

Following the 2006 Second Lebanon War, Israel protested to the Kremlin over the use of Russian anti-tank missiles by Hizbollah. Similar missiles have since reached also Hamas in Gaza.

"The local arms industry certainly didn't like him," said a senior Israeli defence official. "Since he is a native Russian-speaker and an expert on airborne systems, he was a major nuisance for them. It's not surprising that they did everything to frame him."