"The threat is maximal," Manuel Valls said in an interview with the Europe 1 radio station. "We have seen it again in the past few days, the past few hours, and even as we speak. Every day intelligence services, police and gendarmerie thwart attacks and dismantle Iraqi-Syrian networks."
Valls said authorities were monitoring around 15,000 people in France who they believe are in the process of radicalization. Earlier, French officials had said 10,000 people were on their "fiche S" list, used to flag radicalized individuals considered a threat to national security.
"We have almost 700 jihadists -- French or French residents -- fighting in Iraq and Syria, " Valls said.
"Out of these 700 jihadists, I'd like to remind (people) that there are 275 women and several dozens (of) minors," he added. An additional 196 French jihadists died in Iraq and Syria, he said.
On Saturday, French authorities arrested a juvenile on suspicion of preparing an imminent terror attack involving "knives" and "bladed weapons," a source told CNN.
The prime minister's warning of imminent attacks also follows last week's thwarted ISIS plot to attack the Notre Dame Cathedral in Paris
On Saturday, French authorities charged a woman whose name was given as Ornella G, in connection to the plot. She was charged with "terrorist criminal association to commit crimes against people" and "attempted assassinations as an organized gang in connection with a terrorist enterprise," according to the Paris prosecutors' office.
Ornella G and three other women were arrested after a car containing five gas cylinders was found abandoned near the cathedral, a major tourist draw in central Paris.
Paris prosecutor Francois Molins said Friday the women were part of a cell directed by ISIS from Syria. One of the women had a letter in her purse swearing allegiance to ISIS
, Molins said. Another woman had been engaged to be married to two known terrorists.
That woman, named as Sarah H., was due to marry Larossi Aballa, the man who killed two police officers in Magnanville, France, in June
, according to Paris prosecutor Francois Molins.
When Aballa was shot by police, she was then supposed to marry Adel Kermiche
, who killed a priest in Saint Etienne du Rouvray, France, in July. Kermiche was also killed.
French Interior Minister Bernard Cazeneuve said earlier this week that the women were radicalized and likely had been planning an "imminent and violent" attack.
France has been under a state of emergency since the Paris terror attacks in November
, and authorities have struggled to monitor thousands of domestic radicals on their radar.