Valls visited the crime scene, the Kurdistan Information Center in Paris, and promised French law enforcement authorities would track down the killers with "determination," Radio France Internationale reported.
"Three women have been shot, killed, without doubt executed," Valls said. "That's serious and that's why I'm here. It's completely unacceptable."
The Kurdish Associations Federation in France said one victim, Sakine Cansiz, was "one of the founders of the PKK," the Kurdistan Workers' Party terrorist group fighting in Turkey since 1984.
The second victim, Fidan Dogan, worked at the center and the third, Leyla Soylemez, was described as a "young activist," RFI said.
The three women were alone in the center in an area where many Kurds live beginning about midday Wednesday, said Leon Edart, the facility's director. When someone tried unsuccessfully to contact them later, people broke through the door after seeing bloodstains on it, discovering the bodies.
Authorities said two women were killed by a shot to the neck and the third was shot in the stomach and forehead.