White phosphorus burning on the ground. They are using it as a smokescreen. Its a bit strange because there is some sort of cluster barrage just as the smoke covers. I would guess once the smoke was laid and seen to be at max extent, SNA dropped a lifting barrage both to let the troops know its time to move and at the same time put the enemy's heads down.

This is probably a SNA clearance operation because of the fairly heavy weapons possibly including air, and the targeting of fortified buildings.