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 6 am (0300 GMT) deadline passed. Assaults on restive neighbourhoods 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."     

At the United Nations, Annan was to brief the deeply divided Security Council at 1400 GMT. 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.

The 13-month crisis has pushed pressure waves out along faultlines that criss-cross the Middle East, pitting Sunni Arabs against Shi'ite Iran, and alarming Turkey, whose prime minister on Thursday cited his country's right to call on its Nato allies to defend a border where Syrian troops opened fire this week.

People contacted in the flashpoint provinces of Homs, Hama and Idlib, which saw sustained shelling by Assad's forces over the past week, reported calm. Damascus too seemed quiet.

The Syrian government bars access to most independent media. "Snipers, tanks and soldiers are still there. They haven't gone anywhere," said an activist in Homs named Yazan. "People are wary and they believe that this ceasefire is only temporary.      "Nobody is leaving their home."

Burhan Ghalioun, exile head of the opposition Syrian National Council (SNC), told Reuters he expected demonstrations on Friday after weekly prayers - a feature of the revolt that had been subdued by violence in recent months. But he did not trust the authorities who had their "hand on the trigger".

"The Syrian people will go out tomorrow in the biggest possible numbers so that the Syrian people can express their will," Ghalioun said. "While we call on the Syrian people to protest strongly... we ask them to be cautious because the regime will not respect the ceasefire and will shoot."

A Norwegian general who has spent the past week in Damascus discussing a planned UN peace observer mission said he was "cautiously optimistic". But Major-General Robert Mood, who was briefing Annan in Geneva, told Norway's NTB news agency: "Both sides are plagued by a very high degree of mutual suspicion.

"It's terribly difficult for them to cross that abyss."  - Reuters