United Nations - The Syrian war has reached "unprecedented levels of horror", UN envoy Lakhdar Brahimi said on Tuesday after dozens of men were killed in a grim new massacre.
Brahimi told the divided UN Security Council that it must now act to halt the carnage epitomised by the nearly 80 young men, each killed with a single bullet and dumped in a river in the battlefront city of Aleppo.
Syrian rebels blamed President Bashar Assad's government for the killings, but state media said an Islamist opposition faction was to blame.
Syria "is breaking up before everyone's eyes. Only the international community can help, and first and foremost the Security Council", Brahimi told the council's 15 ambassadors.
Twenty-two months of conflict have now left well over 60 000 dead, according to the United Nations, which on Wednesday will seek $1.5bn humanitarian funding for beleaguered Syrians at a conference in Kuwait.
"The tragedy does not have an end," Brahimi said.
The Assad government's legitimacy has been "irreparably damaged", Brahimi said, warning however that it could still cling to power.
Assad's forces have become more repressive, the former Algerian foreign minister was quoted as telling the closed meeting, but he added that both the state and the rebel opposition were committing "equally atrocious crimes".
He also warned of the conflict spilling over into neighbouring countries.
"Syria is becoming a playground for competing forces," Brahimi declared. "None of the neighbours is immune to the fallout consequences of the conflict."
The Security Council has been paralysed on Syria for more than a year. Russia and China have vetoed three Western-drafted resolutions which would simply have threatened sanctions.
Russia accuses the West of seeking regime change through force and insists it cannot make Assad stand down. The United States and its allies back the opposition stance that there can be no talks with Assad.
Brahimi went from the meeting to dinner with the ambassadors of the five permanent council members but US ambassador Susan Rice said "the same issues that have stymied the council to date remain unresolved, so there is no obvious way forward".
In Aleppo, rebel fighter Abu Seif said 78 bodies had been retrieved from the Quweiq River and that 30 more were still in the water but could not be reached because of the threat of Assad snipers.
Hundreds of distressed people watched as muddied corpses were dredged from the Quweiq.
"The regime threw them into the river so that they would arrive in an area under our control, so the people would think we killed them," Abu Seif said.
Volunteers heaped bodies on a truck, which drove them to a school, where they were laid out and covered.
"We do not know who they are," one volunteer said. "They were not carrying papers."
A government security official blamed "terrorists" - the regime term for the rebels - for the carnage. The official SANA news agency said the jihadist Al-Nusra Front was responsible.
Al-Nusra, which has gained notoriety for its suicide bombings, has become a key fighting force, leading rebel attacks throughout the embattled country.
Its suspected affiliation to the al-Qaeda offshoot in Iraq has seen it added to the US list of terrorist organisations.
"The suffering of men, women and children has reached unprecedented levels across the country," said a statement from the International Committee of the Red Cross.
"With no end in sight to the fighting, the humanitarian situation in Syria keeps deteriorating," it added.
January's harsh weather conditions had "not only deepened the misery of displaced people" but made it harder for aid convoys to get through to them.
On the eve of the donors' conference in Kuwait, US President Barack Obama announced an extra $155m to aid refugees fleeing what he said was "barbarism" propagated by Assad's government.
Charity organisations pledged $182m for Syrians.
Kuwaiti press reports say the Gulf state's emir, Sheikh Sabah al-Ahmad al-Sabah, will announce a pledge of $500m at the meeting to be attended by UN Secretary General Ban Ki-moon.