A man armed with a knife and a hammer has left three people injured in an early morning attack at the Gare de Lyon train station in Paris.

It marks another nerve-rattling security incident in the Olympic host city before the Summer Games open in six months.

The 31-year-old man, who was carrying residency papers from Italy and medicines suggesting he was undergoing treatment, was quickly taken into police custody following the attack at 7.35am (6.35am GMT) in one of the bustling station’s halls, authorities said.

France Attack
Investigators work inside the Gare de Lyon station following the attack (AP)

Millions of passengers ride the transport hub’s high-speed trains that link Paris to other cities and its commuter train services to the suburbs and towns in the Paris region.

Laurent Nunez, the Paris police chief who is also in charge of the security operation for the July 26-August 11 Olympics, said: “This individual appears to suffer from psychiatric troubles.”

While stressing that the police investigation is still in its early stages, Mr Nunez said: “There are no elements that lead us to think that this could be a terrorist act.”

Soldiers on patrol
Soldiers patrol outside the station (AP)

A man was seriously wounded in the stomach and underwent surgery and two other people were more lightly hurt, authorities said.

Passers-by helped railway police officers detain the suspect, Mr Nunez said.

He said the man was carrying residency papers delivered in Italy, allowing him to travel legally to other European countries.

The Paris prosecutor’s office said the man is thought to be from Mali in north-west Africa and that the police investigation is looking at a potential preliminary charge of attempted murder.

Soldiers patrol the station
Three people were injured, one seriously, in the incident (AP)

Posting on social media, French interior minister Gerald Darmanin described the attack as an “unbearable act”, and thanked those who detained the assailant.

Security in Paris is being ramped up as it prepares to welcome 10,500 Olympians and millions of visitors for the first Olympic Games in a century in the French capital.

The Games are to open with a massive open-air ceremony along the River Seine on July 26, a major security challenge in the city that has been repeatedly hit by terror attacks, most notably in 2015.

Most recently, a man targeted passers-by near the Eiffel Tower in December, killing a German tourist with a knife and injuring two others.