The Paris prosecutors' office says an investigation has been opened after one of the hostages in the January attacks around Paris accused some television and radio stations of having put his life in danger and sued them.

Twenty people were killed, including the three attackers, in the Islamic extremist attacks around Paris that ended with police raids on a printing plant and a kosher supermarket where hostages were being held.

At the printing plant north of Paris, hostage Lilian Lepere was hiding in a cupboard under a sink, apparently unknown to the gunmen, when at least three television and radio stations revealed his possible presence. He was eventually released unharmed.

Lepere's lawyer, Antoine Casubolo Ferro, said the complaint aims to increase media awareness of life-threatening situations.

"Delivering information without careful consideration may lead to endanger other's lives. Journalists must think of it," he said.

On Jan 9, as the police surrounded the printing plant, lawmaker Yves Albarello revealed on radio station RMC that an employee was hiding in the building.

Later, Lepere's sister Cindy confirmed in an interview to public television station France 2 that she believed her brother to be in the plant and that the family had stopped calling him in order to not compromise his hiding. A TV journalist also reported the information.

In February, France's broadcasting watchdog issued formal warnings to 16 French television and radio stations over their coverage of terrorist attacks, hostage-takings and police standoffs.