But many Syrian opposition leaders operating outside the country say they have little faith that the regime of President Bashar al-Assad will agree to lay down their weapons for the four-day holiday, based on past experience.
Brahimi announced Wednesday that a ceasefire had been brokered between the Syrian government and some rebel groups, but said he expected the regime would release a statement either later that day or Thursday.
The 15-nation UN Security Council endorsed the idea of a temporary truce, with the aim of setting up talks on ending the country's 19-month-old uprising against Assad's governing regime. More than 20,000 people have been killed in the conflict, mostly civilians, according to the UN. But activists estimate the fighting has killed more than 35,000 people.
"We hope that they both realize the importance of a pause in the fighting ... in the symbolic quieting, the silence of the guns," Jan Eliasson, the UN deputy secretary general, said Thursday. "But the most important thing is that it could perhaps create a political environment, where political talks are possible."
Rebel groups' response divided
But media reports from inside Syria suggest a fractured response from the rebel fighters, according to the CBC's Margaret Evans. Some factions in Aleppo, Syria's largest city, say they would agree, but only if prisoners are released and government troops pull back, she reported from Beirut.
Other groups have been demanding an end to the siege in Homs — one of the flashpoints in the conflict — but few expect Syrian forces to withdraw from the central city, Evans said.
On Thursday, activists in Aleppo said there were heavy clashes around the city, particularly around a military airport.
A rebel commander, Bassam al-Dada, told The Associated Press on Thursday that anti-regime fighters have taken two central areas in the country's largest city, including Salaheddin, where battles have raged for months.
UN rights probe into Syria seeks meeting with Assad
Earlier this week, the Syrian government announced an amnesty for all crimes committed before Oct. 23 — except those carried out by "terrorists," it said. The Syrian regime has used this term when referring to the rebels fighting against its government.
On Thursday, nine aid agencies and international human rights organizations issued a statement saying that amnesty must extend to "peaceful activists" in Syrian jails to include journalists, lawyers and doctors.
"Security forces should not use the expansive powers of the country’s Anti-Terrorism Law to exclude peaceful activists, human rights defenders, humanitarian workers and other political detainees from the amnesty," said the statement, released by groups including Human Rights Watch and Reporters Without Borders.
An independent panel probing alleged war crimes in Syria says it is demanding a meeting with Assad as soon as possible.
The head of the panel, Brazilian professor and diplomat Sergio Pinheiro, said the members are seeking the meeting with Assad "without any conditionalities."
The UN's top human rights body has asked Pinheiro and the three other panel members, including renowned former UN war crimes prosecutor Carla Del Ponte, to continue to investigate at least until next March.
Del Ponte, a former Swiss attorney general, said the probe is looking into suspected "crimes against humanity and war crimes, of course" during Syria's increasingly bloody civil war.