Police on Friday said someone has stolen a plaque honouring German resistance to the Nazis from Adolf Hitler's former command headquarters in northern Poland.

The metal plaque was unveiled at the dictator's "Wolfsschanze" (Wolf's Lair) in the village of Gierloz in 2004 to mark 60 years since a failed bomb plot against Hitler by members of the Germany military, namely Colonel Claus von Stauffenberg.

The unknown thief or thieves unscrewed the 60 by 60 centimetre (24 by 24 inch) plaque and likely walked out with it during the night over the weekend, according to Monika Danielak, police spokeswoman in the neighbouring town of Ketrzyn.

"Witnesses said there were German tourists at the site in Gierloz at the time and could help clarify what happened," she told AFP.

"We plan to seek assistance from German police."

The Wolfsschanze was the largest of 10 command bases used by Hitler across Germany and occupied Europe after World War II began with the Nazi and Soviet carve-up of Poland in September 1939.

Every year, some 200,000 tourists visit the 250-hectare (618-acre) site featuring ruined concrete bunkers that could house up to 2,000 people and now lay overgrown in a forest.

It is at the Wolfsschanze that the aristocratic von Stauffenberg tried to assassinate Hitler with a briefcase bomb in July 1944.

The bomb killed three officers and the stenographer but the Fuhrer escaped with only light injuries. Von Stauffenberg and three others were executed that same evening.