A Polish historian on Friday claimed he had found the Amber Room, a long-lost Russian treasure looted by the Nazis during the Second World War.

Bartlomiej Plebanczyk said he believed he had located the missing artwork in a German wartime bunker in north-eastern Poland.

Radar tests showed there was a secret chamber at the back of the bunker where the treasure could be hidden, he said.

The claim comes after two treasure-hunters said they had discovered a Nazi gold train hidden in Poland last year — only for an extensive search to find no trace of it.