French Interior Minister Gerald Darmanin said on Twitter that several people, including children, were wounded in the attack, which took place in the town of Annecy.
He added that the attacker was quickly arrested.
Darmanin and Prime Minister Elisabeth Borne are both headed to Annecy, broadcaster BFMTV announced.
While no official number of injured children has been released yet, it is four, according to BFTMV, and six according to the daily 20 Minutes.
After hearing the news, members of the French parliament observed a minute of silence.