A knife attack occurred early on Wednesday at Paris’s international Gare du Nord station, leaving six people hurt, including one who is critically injured.
The man was stopped, according to Interior Minister Gerald Darmanin, by two police officers who were not on duty but were heading home after a shift.
He claimed that the alleged assailant had been shot three times and was taken to the hospital with serious wounds.
Authorities are attempting to determine whether the attack had a purpose.
The attack took place at 06:42 (05:42 GMT) – within one minute all six people were injured and the attacker was stopped.
Mr Darmanin thanked for police for their “brave and effective” intervention, which he said saved many lives.
He added that among the injured was one border force officer.
Police are yet to name the man, who did not have identity documents on him at the time he was taken to hospital.
Criminal investigators have taken control of the case for now, rather than anti-terror police, Mr Darmanin said.
The incident caused major delays to trains at the station in the early morning rush, with police cordoning off the station and setting up large white curtains around the attack scene.
Paris Gare du Nord is one of the busiest international railway stations in Europe – with about 700,000 travellers a day.