BEIRUT - Syrian troops held their fire in the hours after a UN-backed ceasefire took effect at dawn on Thursday, casting a silence over rebellious towns they had bombarded heavily in recent days. But the lull did little to convince opposition activists and Western powers of President Bashar al-Assad's good faith in observing a peace plan agreed with international envoy Kofi Annan. In defiance of that deal, Syrian troops and tanks were still in position inside many towns, activists told Reuters. The exile opposition, calling the truce "only partially observed" due to that failure to withdraw, urged a renewal of mass protests on Friday. But it warned those taking to the streets, after months when once weekly rallies have been subdued by fear, that they could expect government forces to open fire. The Interior Ministry urged rebels to surrender, promising to free those who had not killed, and broadcast an appeal to the thousands who fled battered cities like Homs and Hama to return from the havens they found in Turkey, Lebanon and within Syria. But streets in troubled towns remained nervously empty and, in one clear report of violence after the ceasefire, activists said security forces shot a man dead at a checkpoint in Hama. "It was a bloody night. There was heavy shelling on the city of Homs. But now it is calm, and there is no shooting," said Abu Rami, an activist in Syria's third city after the deadline passed. Assaults on restive neighborhoods had become more intense after Assad accepted Annan's timetable. Government spokesman Jihad Makdissi said Damascus was "fully committed" to Annan's success and, as there had been no attack on the troops, "There is no reason to break the ceasefire." Western powers, though hesitant to intervene militarily, are lobbying Russia, a key ally for Assad, to drop its veto on other U.N. measures to pressure Syria into abandoning four decades of autocratic rule by his family.