Loud explosions reverberated across the central Syrian city of Homs and clashes were reported in several areas across the country Wednesday, just hours after the government said it has started to withdraw troops from some cities in compliance with an international cease-fire plan.

Activists said troops were carrying out raids and sweeping arrests in suburbs of the Damascus capital and denied that troops were pulling back.

A Syrian government official said Tuesday evening that troops had started pulling out from some calm cities and heading back to their bases, a week ahead of a deadline to implement U.N.-Arab League envoy Kofi Annan's truce plan.

"Forces began withdrawing to outside calm cities and are returning to their bases, while in tense areas, they are pulling out to the outskirts," the government official told The Associated Press in Damascus without saying when the withdrawal began. He spoke on condition of anonymity because he was not authorized to talk to the media.

President Bashar Assad agreed just days ago to an April 10 deadline to implement Annan's plan. It requires regime forces to withdraw from towns and cities and observe a cease-fire. Rebel fighters are to immediately follow by ceasing violence.

In Homs, a bastion of dissent to Assad's regime, opposition figure Mohammed Saleh said there have been a series of loud blasts that "rattled windows" in his home, and that heavy machine gun fire was heard across parts of the old city.

The source of the explosions was not immediately clear, he said. In recent days, armed defectors known as the Free Syrian Army have taken control of the national hospital in the Jouret al-Shayah district and two other government buildings.

"There is no sign of any withdrawal or calm in Homs," Saleh said. "The situation is just as bad as it has been for the past few months."

In the Damascus suburb of Douma, activist Mohammed Saeed said regime troops were carrying out raids and arrests on Wednesday. He said tanks and checkpoints remain in place and reported overnight clashes in the suburb of Kisweh and Moaddamiyeh.

"It is impossible for the regime to withdraw from towns and cities because if it did, we would be in Damascus on the next day," Saeed said.

Opposition activists had charged earlier that the regime was racing to crush opponents ahead of the cease-fire deadline by carrying out intense raids, arrests and shelling on Tuesday.

The opposition has blasted Annan's plan as too little, too late and are particularly angry that it does not call for Assad to leave power _ the central demand of the uprising. They suspect Assad will manipulate the plan and use it to stall for time while his forces continue to crack down.

The Syrian government has not commented publicly on the April 10 deadline. It has accepted other peace plans in recent months only to ignore them on the ground. An Arab League effort that included sending in monitors to promote a cease-fire collapsed in violence in November.