PARIS — France bombed the Syrian city of Raqqa on Sunday night, its most aggressive strike against the Islamic State group it blames for killing 129 people in a string of terrorist attacks across Paris only two days before.

President François Hollande, who vowed to be “unforgiving with the barbarians” of the Islamic State after the carnage in Paris, decided on the airstrikes in a meeting with his national security team on Saturday, officials said.