The government of regional transport hub Dubai said airlines based in the United Arab Emirates would stop flying to Syria, part of a decisive break with Assad's government among countries in the Middle East after eight months of violence.
The news came as Syria's biggest trading partner Turkey suspended all financial credit dealings with it and froze its government's assets.
But Ankara has said any sanctions would not hurt the Syrian people and has ruled out cutting off electricity and water supplies. It has also said civil aviation by Turkish Airlines to Damascus will continue.
Dubai said UAE carriers would stop flying to Syria next week. Dubai-based Emirates and Abu Dhabi-based Etihad are two of the region's biggest airlines.