Syria army 'to observe ceasefire' over Eid al-Adha
Syria's military says it will adhere to a four-day ceasefire to begin on Friday for the Muslim holiday of Eid al-Adha.
The truce will begin at 0600 (0400GMT), reported Syrian TV, adding the army would retaliate against rebel attacks.
The truce was proposed by UN and Arab League envoy Lakhdar Brahimi, who hopes it will lead to a peace process.
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.
Mr Brahimi has travelled across the Middle East over the past two weeks to promote his plan, and on Wednesday won the support of the UN Security Council.
He also said most opposition groups would back the truce, though some rebels have expressed scepticism about the chances of a ceasefire working.
On Thursday, a statement from the Syrian armed forces carried by state media said: "Military operations will cease across the entire Syrian territory as of 06:00 (03:00GMT) on 26 October until 29 October.
"Syrian armed forces will, however, reserve the right to reply to terrorists attacks, attempts of armed groups to reinforce or resupply, or attempts to infiltrate from neighbouring countries."
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 news agency.
Previous attempts at ceasefires in Syria have collapsed, and the violence has continued to escalate.
The US welcomed the ceasefire, and UN Secretary General Ban Ki-moon said he hoped it would lead to political negotiations.
The uprising against President Bashar al-Assad's government started in March 2011.
Activists say more than 35,000 people have been killed since then, while the UN estimates that at least 20,000 have died.
In Aleppo on Thursday, eyewitnesses and activists said government forces had moved away from military posts in the Christian district of al-Seryan and the neighbouring Kurdish area of Ashrafiyeh.
Rebel fighters had reportedly moved in, although there were also reports of continuing fighting.
"The centre of the city is right now in the hands of the Free Syrian Army," an activist going by the name of Marwan told the BBC World Service.
He said the rebels had placed snipers on rooftops to try to prevent government troops retaking the area.
A rebel spokesman was quoted as saying opposition fighters had also taken the south-western neighbourhoods of Salah al-Din and Suleiman a-Halabi.
Meanwhile in Geneva, an expanded team of UN human rights investigators said it had sought a meeting with Mr Assad.
Carla del Ponte, a former UN prosecutor who led the case against former Yugoslav leader Slobodan Milosevic and recently joined the Syria commission, said she saw parallels with her earlier work.
"The similarity of both is that we are handling the same crimes: crimes against humanity and war crimes, for sure," she said.
"My main task will be to continue the inquiry in the direction of determining the high-ranking political and military authorities responsible for these crimes."