Francois Hollande has vowed a “merciless” response to shootings and suicide bombings that killed at least 127 people in Paris.
The French President said the “barbarians of Isis” were responsible for the attacks on a football stadium, rock concert and restaurants and bars around the capital.
Speaking after an emergency meeting of senior government and security officials at the Elysee Palace, Mr Hollande declared three days of national mourning after the “act of war”.
He said the attacks were “committed by a terrorist army, the Islamic State group, a jihadist army, against France, against the values that we defend everywhere in the world, against what we are: a free country that means something to the whole planet”.
The atrocity was "prepared, organised and planned from abroad, with complicity from within the country", he added.
France “will be merciless toward the barbarians of Islamic State group”, Mr Hollande said, and “will act by all means anywhere, inside or outside the country”.
Mr Hollande said the French army and security forces were mobilised “at the highest possible level” and insisted France would “triumph over barbarity”.
“What we are defending is our country, but more than that, it is our values,” he added.
Police were hunting possible accomplices to eight gunmen, wearing explosives belts, who targeted the Stade de France, Bataclan concert hall and bars and restaurants in the 10th and 11th arrondissements.
Disneyland Paris was shut, protests were banned and museums and public buildings were closed across France today after a national state of emergency was declared.
It is believed to be worst night of violence in the country since the Second World War.
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies