The international community waited Thursday to hear if Syria's regime would agree to a truce for a Muslim holiday, as rebel forces moved into new areas of Aleppo and fighting raged across the country.
UN-Arab League peace envoy Lakhdar Brahimi has said Syrian President Bashar al-Assad is ready to observe a truce during the four-day holiday of Eid al-Adha that begins Friday, but the rebels and Washington have been wary of any commitment from Damascus.
If agreed, a ceasefire would mark the first real breakthrough in halting -- even temporarily -- the 19-month conflict that rights groups say has killed more than 35,000 people.
But there were no signs of a slowdown in the fighting on the eve of the holiday, with rebels moving into a strategically important Kurdish neighbourhood in the main battleground city of Aleppo.
Residents in Aleppo's Ashrafiyeh district -- a key area in the heights of the city on a route between its central and northern parts -- said about 200 rebels had moved in to the area for the first time.
One 28-year-old resident said the rebels, who arrived on vehicles mounted with heavy machineguns and bearing the markings of the Liwa al-Tawhid main rebel unit, made it clear they were settling in for Eid despite the promises of a ceasefire.
"Snipers have set up in the buildings and 50 armed men, dressed in black and wearing headbands with Islamic slogans, entered a school near me. I heard them tell the residents: 'We are here to spend Eid with you'," he told AFP.
"I am waiting for things to calm down before leaving," he said.
Rebels and troops were also locked in fighting in the mainly Christian district of Seryan just south of Ashrafiyeh, according to residents.
Fighting elsewhere saw rebels take control of a military post in the northeastern province of Raqa, regime forces bombing the Damascus suburb of Harasta and battles in the capital's southern areas of Tadamun and Qadam, the Syrian Observatory for Human Rights said.
The watchdog gave an initial toll of 42 people -- 26 civilians, 10 soldiers and six rebels -- killed on Thursday across Syria, including 12 by mortar fire in Aleppo's Ashrafiyeh.
Brahimi's assertion that the regime is ready for a ceasefire was backed up by Russia, though Syria's foreign ministry said a final decision would only be taken on Thursday.
The main rebel force, the Free Syrian Army, has said it will only agree to the temporary truce if regime troops cease fire first and that it doubts Damascus will stand by any commitment.
But other rebels groups have refused to accept the proposal, with the radical Islamic Al-Nusra Front saying it will not lay down its weapons and denouncing the truce as a "trick".
The United States has also voiced scepticism, with US envoy to the UN Susan Rice saying many would doubt the regime's word "given Assad's record of broken promises".
Still, Brahimi, a veteran Algerian diplomat, stressed that "if we succeed with this modest initiative, a longer ceasefire can be built" that would allow the launch of a political process.
A ceasefire announced by his predecessor Kofi Annan in April failed to take hold.
Brahimi said he wanted the ceasefire to help create political space for dialogue and for aid to flow in, particularly to the cities of Aleppo in the north, Homs in the centre and Idlib in the northwest.
But elsewhere the international community was boosting pressure on the regime, with UN rights investigators saying in Geneva they would go after high-ranking officials responsible for atrocities.
Renowned former war crimes prosecutor Carla del Ponte, who has yanked out of retirement last month to join the UN Commission of Inquiry on Syria, told reporters that without a doubt "crimes against humanity and war crimes" were being committed in Syria.
Del Ponte said she was focusing on determining "the high-ranking political and military figures (responsible for) these crimes".
The UN investigators also said they had sent a letter to Assad seeking access to the country, after being barred from seeing the conflict first-hand since the commission was created just over a year ago.
Russia on Thursday meanwhile accused Washington of "coordinating" deliveries of arms to Syrian rebels, despite assurances by the State Department that the United States provides no lethal assistance.
"Washington is aware of the deliveries of various weapons to illegal armed groups active in Syria. Moreover, judging by the declarations of US officials published in US media, the US coordinates and provides logistical assistance in such deliveries," the foreign ministry said in a statement.