French President Francois Hollande on Saturday accused the Islamic State (EI) of the wave of bombings on Friday night in Paris that left at least 128 dead and 250 injured, and called "act of war".
"What happened yesterday is an act of war (...) committed by Daesh (Arabic acronym EI) organized from outside and internal complicities established research," said Hollande at the Elysee.
The jihadist group has not claimed responsibility for the attacks.
French President denounced an "act of absolute barbarism", after meeting with key government ministers.
"France will be relentless," said Hollande, who said decreed overnight "all measures to ensure the security of citizens under the state of emergency was taken."
"The internal security forces and the army was mobilized are the highest level of their ability" and "all the safety devices have been reinforced," he said.
"Families are sad and distressed. The country is sad, "said the head of state, before announcing his decision to establish three days of national mourning, but did not say from when.
Hollande also announced Monday that he will appear before the French Parliament in the Congress of Versailles, near Paris, "to unite the nation at this critical moment." This procedure is unique in France.
"What we are defending is our homeland, but also much more, are the values of humanity, and France will know to take their responsibilities," said the president, who called for "unity" and "cold blood" to the French.