Syria's war has descended into "unprecedented levels of horror" the UN's envoy has warned, saying it is only the international community that can help the beleaguered nation.
Lakhdar Brahimi told the divided UN Security Council it must act in the wake of the massacre of at least 71 young men and at least one boy as young as 12, with bodies found dumped in a river in Aleppo, after being executed by Bashar al Assad's forces.
A man reads the Qu'ran next to the bodies of Syrian civilians
The Syrian government has denied responsibility and says the men were executed by an Islamist faction. State news agency SANA said the perpetrators were the jihadists Al Nusra Front.
Brahimi said: "Syria is breaking up before everyone's eyes. Only the international community can help, and first and foremost the Security Council."
He warned that the Assad regime was "irreparably damaged" but said it would be hard to shift the regime from power, and both sides were guilty of "atrocious crimes."
In a gruesome video posted online, 51 muddied male bodies can be seen lying along what appears to be the Queiq River in Aleppo's rebel-held Bustan al-Qasr neighbourhood.
Lakhdar Brahimi, the UN's envoy to Syria
Some of the young men are dressed in casual jeans and trainers. In another video, the bodies are seen wrapped in blue bags, as locals search among the dead for missing relatives.
Human rights organisations and the UN estimates that more than 60,000 people have been killed in the conflict.
The Britain-based Syrian Observatory for Human Rights, a Syrian opposition group, said the Aleppo victims were found with their hands bound and a single, execution-style, bullet wound to the head.
On Monday, the UN warned it would not be able to help millions of Syrians affected by the fighting without more money and will appeal for aid at a conference in Kuwait this week.
Men collect the corpses of men found next to a river, in the neighborhood of Bustan al-Qasr in Aleppo, Syria
Kuwait Emir Sheikh Sabah al-Ahmad al-Sabah has already pledged £150m in aid for Syrians, according to Al Jazeera.
But Médecins Sans Frontières warned that the current aid was going to government-controlled areas, and needs to be distributed more evenly.
Separately, the Lebanese newspaper Al Akhbar, which has close ties to the Syrian regime, claimed on Monday that President Bashar Assad's wife Asma is pregnant with her fourth child, quoting unidentified "visitors" to the Assad family who tipped off the paper.
Syria's first lady has largely remained out of the public eye since the beginning of the Syrian conflict in March 2011.