The suspect was arrested after the train stopped in Arras
A gunman has opened fire with an automatic weapon on a high-speed train travelling from Amsterdam to Paris, wounding three people, two of them critically.
The suspect was arrested after the train stopped in Arras, 115 miles north of Paris, Interior Ministry spokesman Pierre-Henri Brandet said. Passengers were evacuated and police have secured the area.
Investigators from France's special anti-terror police are leading the investigation, a spokeswoman for the Paris prosecutor's office said.
Two of the victims are in a critical condition. The suspect is a 26-year-old Moroccan, said Sliman Hamzi, an official with police union Alliance.
Christophe Piednoel, a spokesman for national railway operator SNCF, said the suspect was armed with an automatic rifle and a knife.
France's interior minister Bernard Cazeneuve is en route to Arras.
He said two American passengers subdued the gunman and one is in hospital with serious wounds.
Mr Cazeneuve said the American passengers "were particularly courageous and showed great bravery in very difficult circumstances" and that "without their sangfroid we could have been confronted with a terrible drama".
A second person was also seriously wounded in the attack while the third is being treated for minor injuries.