Kofi Annan, the joint U.N. and Arab League envoy on Syria, urged Syria's government on Sunday to fully implement its commitment to a cease-fire, and he condemned "a surge in violence and atrocities" that is occurring there.
Annan said in a statement in Geneva that the fighting is causing "alarming levels of casualties, refugees and displaced persons" and that it must stop.
Activists say Syrian troops are continuing their assault on restive regions, despite a plan that calls for government forces to withdraw from towns and villages by Tuesday, and for the regime and rebels to lay down their arms by 6 a.m. Thursday.
But Syria's government appeared to be backtracking on Sunday by demanding written guarantees from its foes to lay down their weapons before withdrawing its own troops.
The commander of the rebel Free Syrian Army, Col. Riad al-Asaad, quickly rejected that demand, saying his group does not recognize Syrian President Bashar Assad's regime and therefore will not give such guarantees.