The war in Syria has reached “unprecedented levels of horror” after evidence emerged of the massacre of dozens of men, the UN envoy for the country has said.

Lakhdar Brahimi told the divided UN Security Council it must act now to prevent further atrocities like the apparent execution of at least 65 men found dumped in a river in Aleppo.

Syrian rebels blamed president Bashar al 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,” Mr Brahimi told the council’s 15 ambassadors.

More than 60,000 people have been killed in 22 months of conflict, according to the UN, which will seek £950m in humanitarian funding for beleaguered Syrians at a conference in Kuwait.

Mr Brahimi said Mr Assad’s government’s legitimacy has been “irreparably damaged” but warned that it could still cling to power as both state and rebel forces commit “equally atrocious crimes”.

He also warned of growing conflict “contamination” in neighbouring countries.

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 Mr Assad stand down. The US and its allies back the opposition stance that there can be no talks with the president.

The Britain-based Syrian Observatory for Human Rights opposition group said the Aleppo victims were found with their hands bound and a single bullet wound to the head – and that the death toll could climb to 80.

Hundreds of distressed people watched as muddied corpses were dredged from the Quweiq river.

“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,” rebel fighter Abu Seif said.

A government security official blamed “terrorists” – the regime term for the rebels – for the carnage.

There was no immediate claim of responsibility, but the official SANA news agency said the jihadist Al Nusra Front carried out the executions.

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 have seen it added to the US list of terrorist organisations.

Aleppo massacre video

[media id=804 width=610 height=340] [adrotate banner=”46″]