A 68-year-old man has been detained by French police in connection with as many as 18 murders between 1980 and 2002.
Most of the victims were gay men. Nicolas Panard was arrested in the French city of Mulhouse yesterday.
He is reported to be well-known on the gay scene and previously worked as a drag performer.
Panard’s alleged accomplice, Slim Fezzani, is already serving a 20-year prison sentence for a separate murder.
Both men deny involvement with the murders and are being questioned by police in the town of Montbeliard, where a local officer had been investigating a 1991 murder.
He discovered Panard’s name in several records of unsolved murder investigations held on a crime database.
The BBC reports that Panard is alleged to have killed 11 people in the Alsace region, four others in neighbouring Franche-Comte, and three near Paris.
It is not thought that detectives have formal proof of the men’s involvement in the murders.
All the victims were killed by blows to the head followed by multiple knife wounds.