A 17-year-old gunman took four hostages in a convenience store on the outskirts of the southern French city of Toulouse for more than four hours before releasing them, police said.
Authorities were not certain what the hostage taker was demanding. No injuries were reported.
The youth seized the hostages at 4.20pm on Tuesday in the town of Blagnac, near Toulouse airport, according to a national police spokeswoman.
The suspect was not known to police, the spokeswoman said, declining to give details of his identity while the standoff was still under way.
The teenager later released all four hostages but remained inside the store, surrounded by police, another police official said.
Local state television France 3 reported that the hostage-taker fired three shots in the air, was wearing a helmet fitted with a camera and demanded to speak with a negotiator.
Police locked down the neighbourhood, evacuating some buildings and ordering other residents to stay inside, according to neighbour Robert Texier.
A police helicopter circled overhead.
The police spokeswoman and a security official said it was too early to rule out terrorism without knowing the hostage-taker's demands.
"It's worrying. It all happened so quickly," said Mr Texier, who expressed surprise at the incident in what he described as a quiet neighbourhood on the banks of the Garonne River.
He said the convenience store has been run for decades by a woman and her daughter who live in the adjacent building.