The Russian Su-27 fighter jet crashed on September 8 near Jurbarkas, some 55 kilometres (35 miles) from Lithuania's second largest city, Kaunas, having entered the Baltic state's airspace without permission. Lithuania joined the NATO defence alliance in March 2004.

"The (onboard) reconnaissance system was triple protected. It would self-destruct automatically when the pilot ejected or at the moment the plane hit the ground," the Russian minister confirmed Wednesday to the news media.

"It is speculation to say that this system could find itself in the hands" of a foreign country, he added.

The jet's pilot Valery Troyanov ejected and has been held by the Lithuanian authorities while an investigation was carried out.

"The investigation (into the crash) is almost finished and the pilot will return to Russia very soon," Ivanov said.

"It is a serious lesson for us all. We will look closely at the mistakes that were made," he added.

The jet was supposed to have followed a route from Russia to Kaliningrad, a Russian exclave wedged between Lithuania and Poland, that would have taken it above neutral waters in the Baltic Sea, but deviated from its path for unknown reasons.

Lithuanian investigators concluded Tuesday that the crash had been caused by pilot error as well as mistakes by Russian air control services.

The head of the Lithuanian air force was fired over his handling of the incident last week.

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