French police on Monday said they had arrested a German national after his wife was discovered after 12 years of captivity in the couple's home.

A police source said the woman, also German, was naked with her head shaved when they found her in a bedroom in the apartment, and had multiple injuries, including broken bones.

She had probably been tortured, the source said.

Police said the bedroom was closed off with metal wire at the residence in Forbach, eastern France, which is close to the German border.

The 53-year-old woman had managed to call police in Germany, who in turn alerted their French colleagues, a police source said.

The source said the woman was believed to have found access to a phone and called police in Wiesbaden, western Germany.

She has been rushed to hospital with fractures in both legs, and her fingers.

The man, 55, was is accused of kidnapping, aggravated rape, and acts of torture and barbarism, French broadcaster BFMTV said.

A police source in the eastern city of Metz, where the man was being held, told AFP that investigators were still piecing together the events.

"Several checks are underway, and I'd like to remain cautious," the source said.

Broadcaster RMC said police found a diary-type notebook in the flat, in which it was believed the man kept a record of his actions, and of the times he gave his wife food.