TEHRAN, Young Journalists Club (YJC) - In the attack next to a canal in the northeast of the capital on Sunday evening, the suspect, believed to be in his thirties, was overpowered by bystanders who had tried to stop him by throwing petanque balls at him.
Unconscious when officers arrived on the scene, the alleged assailant was taken to hospital, police said.
A source close to the case said the man, whose identity was currently being verified, was an Afghan born in 1987.
Though the suspect had targeted foreigners, "nothing at this stage suggests a terrorist attack", a source close to the inquiry added.
Among the seven injured were two British tourists and an Egyptian visitor. On Monday evening, three of injured people were still in hospital, including one in critical condition, another source said.
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 11:00 pm (2100 GMT).
"I saw this guy with a knife who was trying to attack people," an eyewitness, Hamani Bouadjema, told AFP.
"My first reflex was to run after him, and my mates followed. We started throwing our petanque balls at him," Bouadjema said.
One of his friends picked up a plank of wood on the ground and "hit him on the hand in which he was holding the knife," the eyewitness continued.
Then the group "jumped on him and got him to the ground."
The eyewitness said the man "seemed to be on drugs. He seemed to be on something.
He definitely didn't seem normal. He had a blank look... He didn't say anything. Even when we hit him, he didn't shout 'ouch'."
Another eyewitness Youssef Najah, 28, said he was walking beside the canal when he saw a man running and holding a knife about 25-30 centimetres (10-11 inches) 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," he added.