France has urged the United Nations Security Council to immediately convene following Baku's operations.
The French Foreign Ministry said in a statement that no pretext could justify the military operation Azerbaijan launched in Nagorno-Karabakh.
France said the outbreak of fighting "threatens thousands of civilians already affected by a months-long illegal blockade and which runs against efforts by the international community to reach a negotiated settlement."
Paris said it was working with its partners to prepare a "strong response" to what Foreign Minister Catherine Colonna called an "illegal, unjustifiable and unacceptable" operation.
"I would like to emphasize that we hold Azerbaijan responsible for the fate of Armenians of Nagorno-Karabakh," she said.