MOSCOW (Reuters) - Relatives of Swedish war hero Raoul Wallenberg filed a lawsuit in a Moscow court on Wednesday against Russia’s Federal Security Service (FSB), seeking access to uncensored documents which they say could provide clues to Wallenberg’s fate.

Wallenberg, a former Swedish diplomat, helped save thousands of Hungarian Jews during the Second World War before being captured by Soviet forces in 1945.

A Russian report claimed he died in 1947 in the Lubyanka prison in central Moscow run by the Soviet KGB security service, but no definitive proof of his fate has been put forward.

Marie Dupuy, Wallenberg’s niece, said in a statement that Russian archives contained documents with direct relevance for Wallenberg’s fate that neither his family nor independent experts had been allowed to review.

“Our search for answers will continue until we know what happened to Raoul Wallenberg, and why,” Dupuy said in the statement distributed by Team 29, the group representing the Wallenberg family in Russian courts.

The FSB, successor to the Soviet-era KGB security service, did not immediately respond to a Reuters request for comment.