Six French fighter jets have targeted and destroyed an Islamic State training camp in eastern Syria, President Francois Hollande has confirmed.
The air strikes were the first in Syria by France as it expands its mission against IS.
"The camp was totally destroyed," Mr Hollande said after arriving at the United Nations for a major development summit and the UN General Assembly.
"We're sure there were no casualties" among civilians, he added.
The French president's office announced the strikes, without details, in a statement hours earlier.
"Our nation will strike each time our national security is at stake," the statement said.
Mr Hollande told reporters the strikes on the training camp, and others to come, were aimed at "protecting our territory, cutting short terrorist actions, acting in legitimate defence".
He said more strikes "could take place in the coming weeks if necessary".
The targets were identified in earlier French reconnaissance flights and with information provided by the US-led coalition.
The president announced earlier this month a change in French strategy - expanding its air strikes over Iraq into Syria.
France has carried out 215 air strikes against IS extremists in Iraq as part of the US-led coalition since last year, the Defence Ministry said earlier this month. But it previously held back on engaging in Syria, citing concern over playing into president Bashhir Assad's hand and the need for such action to be covered by international law.
Officials now evoke "legitimate defence" as spelled out in the UN Charter to support strikes in Syria.
France has already been attacked by extremists claiming ties to IS. Mr Hollande, who has ruled out sending ground troops into Syria, has cited "proof" of plans for attacks on France and the growing danger to Syrian civilians, with a large chunk of the population fleeing in a massive exodus.
Prime minister Manuel Valls said France is going after IS "sanctuaries where those who want to hit France are trained".