BEIRUT - After months of intensifying bloodshed, an uncertain cease-fire backed by the United Nations and brokered by the special envoy Kofi Annan went into effect in Syria early Thursday with mutual accusations of scattered infractions by the antagonists but none of the by-now-familiar reports of shelling by government forces and mayhem in major cities.
“I am encouraged by reports that the situation in Syria is relatively quiet and that the cessation of hostilities appears to be holding,’’ Annan said in a statement from his Geneva office. “Syria is apparently experiencing a rare moment of calm on the ground.’’
Annan asked the Security Council to authorize the deployment of UN monitors in Syria, assuming the cease-fire holds. Susan E. Rice, the US ambassador to the United Nations and president of the Security Council, said members will meet to negotiate the terms.
“It is our interest and shared aim to negotiate that text as swiftly as possible,’’ Rice said.
Despite the lull in violence, many diplomats remain skeptical about its duration. Both Annan and Rice emphasized that his six-point plan had yet to be implemented and that Syria had not fully complied with a key provision - the withdrawal of troops and heavy weapons from major population centers.
“Mr. Annan was clear that what the Syrian government has done today does not constitute full compliance,’’ Rice said at the United Nations after the council was briefed by Annan via private video link.
Secretary General Ban Ki-moon, who also spoke with Annan Thursday, told reporters while visiting Geneva: “The onus is on the government of Syria to prove that their words will be matched by their deeds.’’
The exiled Syrian National Council opposition, which is seeking the overthrow of President Bashar Assad, said there were reports of raids and arrests of the government’s opponents in some suburbs of Damascus and that it was not clear how long the guns would remain silent.
Several hours after the cease-fire deadline, activists said they were concerned that government troops had not returned to barracks. And, as the day wore on, opposition groups said there had been some tank fire from government forces, but reports of at least one opposition fatality remained unconfirmed.
State media said, however, that an army officer was killed and 24 “officers, noncommissioned officers, and a number of civilians’’ were wounded when rebels bombed a military bus carrying soldiers to work in the northern city of Aleppo, the country’s largest.
The blast was said to have struck at 8 a.m., two hours after the cease-fire began.
The Syrian Defense Ministry in Damascus, the capital, said a decision had been made to observe the cease-fire after government forces carried out “successful missions in combating criminal acts by armed terrorist groups’’ - the term the authorities use to describe their armed adversaries.
But the official SANA news agency, quoting “an official source’’ at the ministry, said that, having “enforced the authority of the state on all its territories,’’ the “armed forces will be on alert to confront any attack by armed terrorist groups against civilians, law-enforcement members, the armed forces, and private and public facilities.’’
The continuing state of alert seemed to corroborate assertions by opponents of Assad that government forces had not pulled back from forward positions in some areas. Additionally, the official assertion that the army had spread state authority across the land seemed to reflect the ferocity of an onslaught in the days leading to the truce, during which activists reported scores killed.
But activists reported no fighting across the country after the deadline for the cease-fire to go into effect passed at 6 a.m.
Abu Rami, an activist reached via Skype in Homs, said there had been no gunfire, shelling, or other attacks for several hours.
A spokesman for the Syrian Observatory for Human Rights, based in Britain, said the calm endured for an hour after the deadline for the cease-fire.
“It is quiet in every region,’’ he said, adding that a few explosions had been heard in Zabadani, just outside Damascus.
Other activists said the explosions there had been heard before the cease-fire.
The cease-fire was supposed to halt violence that started 13 months ago with an uprising against Assad’s rule. Since then, it has turned into the most violent government crackdown on dissent of the Arab revolts against despotic rulers that took root last year. The United Nations estimates that at least 9,000 people have died.
In a first international response to the apparent halt in the fighting, China, which has supported the Syrian government, said it “welcomes the government’s relevant decision, which will help to ease tensions.’’ China also warned the opposition forces to comply with the truce.
While the rebels do not have a unified command structure, their forces were apparently heeding the cease-fire.
Qassem Saad al-Deeb, a spokesman for the Free Syrian Army, one of the main umbrella organizations of the opposition, told Reuters: “We will wait until tomorrow and see.’’