BEIRUT - A UN-backed ceasefire aimed at halting more than a year of bloodshed in Syria appeared to be holding early on Thursday but activists saw no sign that President Bashar Assad was pulling his forces out of restive cities.The flashpoint provinces of Homs, Hama and Idlib, which have been under sustained shelling by Assad's forces over the last week, were calm after the 6 a.m.ceasefire deadline. An activist in Damascus said the capital was also quiet.Ceasefire PledgeSyria's Defense Ministry said on Wednesday it would halt operations on Thursday morning but made no mention of an army pullback from cities and said it would confront "any assault" by armed groupsA spokesman for Annan said on Wednesday night an advance planning team negotiating how UN observers would monitor the accord had left Damascus after a week of talks.He had no further comment on any progress reached by the team led by Norwegian Major-General Robert Mood, so it was not clear whether the deployment had been agreed or called off.Annan is due to brief the UN Security Council on developments in Syria at 1400 GMT.Insurgents, who lack a clearly coordinated command structure, said they would stop shooting if Assad's forces withdrew and observed the truce"The Defense Ministry announcement is a detour on Annan's plan which clearly says he should pull back the tanks and end violence. We will wait until tomorrow and see. We will not act before tomorrow," Qassem Saad al-Deen, Free Syrian Army spokesman inside Syria, told Reuters on Wednesday.At least 12 people were killed on Wednesday, activists said.Western powers have scorned Assad's truce pledges and largely sympathize with the revolt against him, but so far lack an effective policy to curb the bloodshed, given their own aversion to military intervention and the resistance of Russia and China to any UN Security Council action against Assad.Quoting from a letter to Annan from the Syrian foreign ministry, Annan's spokesman Ahmad Fawzi said the government had undertaken "to cease all military fighting throughout Syrian territory as of 6 a.m. (0300 GMT) tomorrow, Thursday, 12 April, 2012, while reserving the right to respond proportionately to any attacks carried out by armed terrorist groups against civilians, government forces or public and private property".He also stressed that troops should pull back.The exile opposition Syrian National Council (SNC) called for an international ultimatum to Assad if he failed to respect the ceasefire."We would like to see a unanimous decision by members of the Security Council that sends an ultimatum to the regime with a deadline that is not too far down the road that says on such and such a date enforcement measures will intervene," SNC spokeswoman Basma Kodmani said on Wednesday.Assad's forces have killed more than 9,000 people in the past year, according to a UN estimate. Damascus says rebels have killed more than 2,600 soldiers and security personnel."More than two hours have passed and it's completely quiet across the country," said Rami Abdulrahman, director of the British-based Syrian Observatory for Human Rights (SOHR).The Syrian government bars access to most independent media.Fighting had raged in the countdown to Thursday's deadline, fueling widespread doubts that Syria would comply with international envoy Kofi Annan's ceasefire plan.World leaders, grappling with fundamental disagreements particularly between the West and Russia over how to deal with the crisis, are monitoring events on the ground closely."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 an activist who called himself Abu Rami, speaking from Syria's third largest city which has endured some of the worst violence.But, like activists in other towns, he said there was no indication that Syrian army forces were withdrawing from Homs in accordance with the ceasefire agreement. "There are no signs of a pull back - the tanks, snipers and armed forces are still visible across the city," he said.The Syrian Observatory reported explosions in Zabadani, a town close to the Lebanese border, shortly after the deadline. But a resident contacted by Reuters said the town was quiet.