The leader of Lebanon's Iran-backed Hezbollah, a key Damascus ally, said on Wednesday his group would keep its military presence in Syria until further notice, commending a Russian-Turkish deal over Idlib as a step towards a broader political solution.

But Sayyed Hassan Nasrallah indicated the number of fighters of the powerful Shi'ite group would be reduced as fronts across Syria become more quiet.

"We will stay there (in Syria) even after the settlement in Idlib. Our presence there is linked to the need and the consent of the Syrian leadership," he said in a televised address to hundreds of cheering followers in southern Beirut on the eve of the annual Ashura religious rally.