Two men armed with kitchen knives killed a 19-year-old man and wounded 9 others in a Lyon suburb, officials said.
Three of the injured are gravely ill, firefighters said.
The stabbings happened close to the Laurent Bonnevay metro station in Villeurbanne,
One suspect was arrested and another was being sought, AFP reported.
Video posted on Twitter purported to show one of the suspects being held by passers-by.