BEIRUT — Syrian government shelling and offensives against rebel-held towns killed at least 53 civilians across the country on Saturday, activists said.

Also, the U.S. posted online satellite images of troop deployments that cast further doubt on whether the regime intends to comply with an internationally sponsored peace plan.

Syrian President Bashar Assad has accepted a cease-fire deadline brokered by international envoy Kofi Annan, which calls for his forces to pull out of towns and cities by Tuesday and for both government and rebels to lay down their arms by 6 a.m. local time Thursday.

But the escalating violence of the past few days has fueled accusations that Assad is rushing to stamp out as much of the year-old uprising against him as he can before next week’s cease-fire.

The Syrian government said it has begun to withdraw forces ahead of the cease-fire but activists say no significant pullouts have taken place and troops, checkpoints and snipers remain in almost all major flashpoint towns and cities.