He also said that Friday’s attacks by Islamist militants in Paris were planned and organised from Syria.
A total of 129 people died in the attacks on bars and restaurants, a concert hall and the Stade de France while 352 others were injured. According to the persecutor, 99 others are in critical condition.
France is to hold a nationwide minute of silence at midday local time for the victims, the BBC reported.
A huge manhunt is under way for surviving members and accomplices of the Islamist group that carried out the attack.
Meanwhile, two more attackers have been named, as well as the five already identified.
Police have named Brussels-born Salah Abdeslam, 26, as a key suspect. He was reportedly stopped by officers in the wake of the attacks – but then let go.
Meanwhile, French aircraft have started retaliatory attacks in Raqqa, the stronghold of the Islamic State group in Syria, which claimed responsibility for Friday’s attacks.
Mr Valls said that France was dealing with a “terrorist army”, rather than a single terrorist group.
“We know that operations were being prepared and are still being prepared, not only against France but other European countries too,” Mr Valls said.
Security forces are conducting raids across France and Belgium.
French Interior Minister, Bernard Cazeneuve, said that 168 raids have been conducted in eight different locations, with arms and cash retrieved.
Authorities said they sieized a rocket launcher in the city of Lyon in one of the raids.