The Islamic State jihadist group claimed gun and bomb attacks that left more than 120 people dead in Paris in a statement posted online on Saturday.
It said “eight brothers wearing explosive belts and carrying assault rifles” conducted a “blessed attack on… Crusader France.”
The statement, published in both Arabic and French, threatened further attacks against France “as long as it continues its Crusader campaign.”
It said the targets of Friday’s attacks, which included the national sports stadium and the Bataclan concert hall, “were carefully chosen”.
It said France was guilty of “striking Muslims in the caliphate with their aircraft.”
France is part of a US-led coalition conducting an air war against IS in Syria and Iraq, where IS declared a caliphate last year after seizing swathes of both countries.
It has carried out air strikes in Iraq for more than a year but extended them to Syria in September.
French President Francois Hollande had already blamed IS, calling the coordinated assault an “act of war… committed by a terrorist army, Daesh, against France”, using another term for IS.
Meanwhile, European Commission President Jean-Claude Juncker and NATO head Jens Stoltenberg both said they were “deeply shocked” by the attacks in Paris Friday that have left at least 120 people dead.
European Council President Donald Tusk said he will ensure the G20 summit in Turkey over the weekend will respond to the threat of terrorism as both he and Juncker prepared to represent the European Union at the event.
On his Twitter account, Juncker said: “I am deeply shocked by the events in Paris. We stand in full solidarity with the people of France.”
In a later message to French President Francois Hollande, Juncker, the former prime minister of Luxembourg, said he was “revolted to see that France is at this same moment hit by the most odious terrorism.”
Writing in French, he added: “I think about the victims, the wounded, the rescue (services). I trust the authorities and the French people to overcome this new ordeal together.”
Other members of the European Commission, the executive arm of the 28-nation European Union in Brussels, have also reacted to the attacks.
EU foreign policy chief Federica Mogherini, also writing in French, tweeted that she “is in the process of following with pain and dread the events in Paris.”
Mogherini, the multi-lingual former Italian foreign minister, added: “Europe is with France and the French people.”
Echoing the commission was Stoltenberg, the NATO secretary general, who said: “I am deeply shocked by the horrific terrorist attacks across Paris tonight.