France has carried out air strikes for the first time against targets associated with the group calling itself Islamic State.
French aircraft have destroyed a training camp in the eastern Syrian city of Deir el Ezzor.
President Francois Hollande is at the UN in New York.
“France launched air strikes in Syria this morning,” he told reporters. “We hit a training camp which could pose a threat to our national security.”
Until now, Paris has refused outright to be involved any action that could help the Assad government.
Observers say this latest policy shift shows combating the militants is a greater priority.
Meanwhile, Russia’s President says Bashar al-Assad deserves international support.
Speaking ahead of a meeting with US President Barack Obama in New York, Vladimir Putin branded US support for anti-government forces in Syria as “illegal”.
World leaders are meeting at the UN in New York and the pressure is on to find a diplomatic solution to the Syrian crisis.
Russia’s increased military involvement in Syria, coupled with the refugee crisis the conflict has provoked in the region and the EU, has added increased urgency.