A heavily armed man opened fire on a high-speed train travelling from Amsterdam to Paris on Friday, injuring two people before being overpowered by two American passengers.

A heavily armed man opened fire on a high-speed train travelling from Amsterdam to Paris on Friday, injuring two people before being overpowered by two American passengers.

The motives behind the attack were not immediately known, although French prosecutors said a probe was being launched by counter-terrorism investigators.

The assailant was arrested after the train pulled into the station in the northern French town of Arras, a spokesman for the French state rail company SNCF told AFP.

According to the initial French investigations, the gunman was known to French intelligence services and was Moroccan or of Moroccan origin and aged 26.

The man was carrying several weapons in his luggage, including guns and razor blades, one source close to the case told AFP, with some reports that he was armed with a Kalashnikov.

"The anti-terrorist section of the prosecutor's office has taken this case, in agreement with the local prosecutor, in view of the weaponry used, the way it happened and the context," the prosecutor's office said.

Commenting on the incident, French President Francois Hollande said in a statement that "everything is being done to shed light" on the shooting.

Prosecutors said the gunman was overpowered by two American passengers.

An American and a Briton were reportedly among those hurt in the attack.

France has been on edge since extremist gunmen attacked the satirical magazine Charlie Hebdo and a Jewish supermarket in Paris in January, killing 17 people.