Thieves have stolen the infamous Arbeit macht frei ("Work will set you free") gate sign from the Nazi-era Auschwitz death camp in Poland, museum staff and police said yesterday.

"The inscription was stolen early this morning," Auschwitz-Birkenau Museum spokesman Jaroslaw Mensfeld said.

"It's a profanation of the place where more than a million people were murdered. It's shameful," he added.

The theft of the metal sign - which was forged by prisoners on Nazi orders, and was one of the most sinister examples of their propaganda - has sent shockwaves across Poland.

"This is horrible," Senate speaker Bogdan Borusewicz told the radio station Jedynka. "I hope the police will recover the sign soon and that it won't have been cut into pieces."

Andrzej Kremer, Poland's deputy foreign minister, told the PAP news agency he was shocked, because the sign was a "key symbol of this death camp".

Ex-President Lech Walesa, the former leader of the communist-era opposition movement Solidarity, said it was "unthinkable".

"But I don't see it as an ideological act. It's a criminal matter. It can't be comprehended any other way," Mr Walesa told the rolling news channel TVN24.

Whoever stole the sign must have known what they were doing, Mr Mensfeld said.

The forged iron inscription was not hard to unhook from above the large gates at the entrance, "but you needed to know how," he explained.

The police have launched an inquiry and the local governor has promised his full support.

Police spokesman Malgorzata Jurecka told the radio station Trojka that the theft had taken place at around 6. 00 a.m. (0500 GMT).

"A police dog has been set on the trail of the thieves," she added.

The site of the former camp, on the outskirts of the southern Polish town of Oswiecim - Auschwitz in German - is closed at night and patrolled by watchmen.