However, he said he understood the public's "strong concerns" and urged "vigilance".
In the latest incident, 10 people were hurt when a van was driven into a Christmas market in Nantes on Monday.
In Dijon on Sunday, a driver shouting "God is great" in Arabic ploughed into pedestrians, injuring 13 people.
On Saturday, a man using the same phrase was shot dead by police after attacking them.
President Francois Hollande has called for an emergency cabinet meeting on Tuesday and urged the public not to panic.
The BBC's Hugh Schofield Paris says French authorities are playing down the idea that there is a pattern behind the three attacks.
However, many people will be asking themselves if there is a copycat element to them, he adds.Mr Valls told Europe 1 radio there was "no link" between the three attacks and that security forces were dealing with individuals who acted alone.
"We do not minimise these acts," he said, adding that the government wanted to "reassure" the public and understand what had happened.
"The best response is to continue to live peacefully with the necessary vigilance of course," he added.
The attack in the western city of Nantes took place at about 19:00 local time (18:00 GMT) with witnesses saying the van drove into a stall selling mulled wine.
After the vehicle came to a halt, the driver stabbed himself in the chest several times, causing himself serious injuries.
French interior ministry spokesman Pierre-Henry Brandet said the motive was not clear."I wouldn't say it was a terrorist attack. I would call it a deliberate act. There's been a heavy toll, about 10 people wounded, five in a serious condition and one of those facing life-threatening injuries.
"As for the motivation for this man, he is an individual we haven't yet identified, the judicial investigation is just getting under way."
Interior Minister Bernard Cazeneuve said the attacker in Nantes seemed to be "unbalanced".
The driver of the vehicle in Dijon was arrested after targeting pedestrians in five different parts of the city in the space of half an hour.
The city's prosecutor said the attacker had a long history of mental illness and the incident was not linked to terrorism.
In Saturday's incident, a man stabbed three police officers in the city of Tours before being shot dead.
Anti-terrorism investigators have opened an inquiry into that attack.
