The Syrian military says it will observe a four-day truce beginning Friday morning for the Muslim holiday of Eid al-Adha.

The truce will begin at 6 a.m. local time (midnight EDT), the BBC quoted official  Syrian TV saying, but the army reserved the right to retaliate against “terrorist” rebel attacks.

The news came as rebels said they had advanced into several central areas in Aleppo, Syria's largest city and a key battleground in recent months.

At least 106 people were killed Thursday amid fighting and shelling nationwide, the opposition Local Coordination Committees of Syria said. At least 36 of them died in Damascus and its suburbs and 33 in Aleppo, CNN reported.

And Damascus residents told Reuters of artillery barrages by government troops hours before the ceasefire. 

 U.N. and Arab League envoy Lakhdar Brahimi, architect of the truce, has travelled across the Middle East over the past two weeks to promote his plan, and on Wednesday won the support of the U.N. Security Council.

Unlike an ill-fated cease-fire six months ago, this truce is not linked to any formal peace plan or call for negotiations. Nor are there any international observers inside Syria to monitor compliance.

Qassem Saadeddine, a spokesman for the joint command of the Free Syrian Army, the main armed rebel group, said his fighters would back the truce.

"But we will not allow the regime to reinforce its posts," he told Reuters.

Some rebel factions have dismissed the truce outright and say they have no intention of laying down their arms, even for four days, the Los Angeles Times reports. Others have publicly backed the plan but insist the military must also not use a pause in fighting to rearm and resupply troops.

The United States and the United Nations welcomed the news, CNN reported.

"What we are hoping and expecting is that they will not just talk the talk of cease-fire, but they will walk the walk -- beginning with the regime," said U.S. State Department spokeswoman Victoria Nuland.

At the United Nations, Secretary-General Ban Ki-moon "welcomes the reported announcements," U.N. spokesman Martin Nesirky told reporters.