Saudi Arabia has joined Qatar in calling for international action in Syria, and has announced it is pulling its members out of an Arab League monitoring mission.
The region's major oil power accused President Bashar al-Assad's regime of using the month-long mission to "hide its crimes".
Prince Saud al-Faisal, the Saudi Foreign Minister, said: "It is not a quality of Arab leaders to kill their people."
The statement overshadowed an Arab League proposal to renew the mission for a further month.
Qatar has called for a review of the mission, possibly leading to the dispatch of Arab troops to act as peacekeepers.