A woman has been found dead after an armed man entered a retirement home for former missionaries near Montpellier, according to French media reports.
Police responded to the incident late on Thursday evening in Montferrier-sur-Lez in the south of the country.
The home for former missionaries to Africa has been evacuated, but the suspect remains at large.
There is so far no indication that this is a terrorist incident, sources close to the investigation said.
A caretaker contacted police after escaping from the home, Reuters
news agency reported.
The body of the dead woman was found gagged and tied up outside the building, an official said.
Police searched the building extensively, but the suspect had fled the scene.
"For the time being, there is only one victim," Montpellier prosecutor Christophe Barret told the AFP news agency. "For the moment there is no particular evidence about the motive for this crime."
The man was not known to authorities.
Residents of the home "are very elderly with an average age of 75 although some are more than 90," a local councillor said, and many need assistance to walk, he said.
French newspaper Le Figaro said that the attacker was "hooded and armed with a knife and sawed-off shotgun" when he broke into the home, citing sources close to the investigation.
The mayor of the town, Michel Fraysse, told the AFP news agency the building housed around 60 former missionaries, six or seven lay people, and another six or seven nuns.
A correspondent for AFP said 15 police vehicles and a dozen belonging to the fire service were stationed a few hundred metres from the building.
Olivier Ribadeau Dumas, a spokesman for the Conference of Bishops of France, tweeted: "our prayers tonight go to the woman who lost her life in this attack on a retirement home."
France remains in a formal state of emergency since a wave of terrorist attacks last year.