Syria's government has claimed it has begun to withdraw troops from calm areas ahead of an April 10 deadline to implement an international cease-fire plan.
Opposition activists say government troops were intensifying their shelling on April 3 in a bid to crush opponents ahead of the deadline.
The competing claims could not be independently confirmed.
The U.S. State Department says it has seen no evidence that any withdrawal has begun.
An advance United Nations team is expected in Damascus by April 5 to discuss the deployment of cease-fire monitors in Syria as part of a peace plan proposed by UN-Arab League envoy Kofi Annan.
If the plan is endorsed by a UN Security Council resolution, some 250 UN observers would be deployed in Syria for the monitoring mission.
With reporting from Reuters and AP