PARIS－Seven people including two British tourists were wounded in Paris late on Sunday by a knife-wielding man, a terrifying attack that bystanders tried to stop by throwing petanque balls at the assailant.

Four of the victims were in a critical condition, police said, after the man brandishing a large blade and iron bar went on the rampage next to a canal in the northeast of the capital.

The suspect is believed to be an Afghan national and has been arrested, said a source close to the enquiry, adding he had targeted "strangers" but that "nothing at this stage shows signs of a terrorist nature".

Chaos erupted on the banks of the Bassin de la Villette, an area popular with locals and visitors who frequent the cafes, cinemas and other cultural venues along its banks, just after 11 pm.

Eyewitness Youssef Najah, 28, said he was walking beside the canal when he saw a man running and holding a knife about 25-30 centimeters long.

"There were around 20 people chasing him. They started throwing petanque balls at him," Najah said, referring to the sport popular in France also known as boules.

"Around four or five balls hit him in the head, but they weren't able to stop him."

According to the same witness, the attacker then dived into an alleyway, where the man "tried to hide behind two British tourists. We said to them: 'Watch out, he has a knife.' But they didn't react".

The pair were then attacked, he said.