An airstrike has hit an aid convoy in Syria, reportedly killing at least 32 people - shortly after a week-long ceasefire came to an end.
The Syrian Red Crescent trucks were hit in Urm al Kubra, a town near Aleppo, Reuters news agency reported.
The British-based Syrian Observatory for Human Rights said at least 32 people were killed in the attack.
The monitoring group said the strike was carried out by either Syrian government or Russian military.
The secretary general of the International Federation of Red Cross and Red Crescent Societies told a UN summit in New York that 14 Syrian Arab Red Crescent volunteers were killed.
'Our outrage at this attack is enormous,' said the UN Special Envoy for Syria, Staffan de Mistura.
A statement uploaded to Facebook by Aleppo activists said: 'Dozens of martyrs and wounded in Aleppo, and 20 vehicles for Red Crescent set on fire in airstrikes.
'Martyrs and wounded among civilians were reported, some of them are still stuck under the rubble, in Aleppo city and its suburbs, due to bombardment and artillery shelling.'
There had been at least 35 airstrikes in and around Aleppo since a US-Russia brokered ceasefire ended on Monday evening, the Syrian Observatory for Human Rights said.
The truce had been put under intense pressure following a series of airstrikes at the weekend and a spat between Moscow and Washington over four US-led airstrikes which mistakenly killed around 60 Syrian soldiers on Saturday.
America apologised for the bombing which occurred on a base near the eastern Deir al Zor airport, insisting their intended target was Islamic State fighters, and Theresa May has admitted Britain played a role in the attack while alleging the British military would never 'intentionally' strike Syrian forces.
It is understood Britain's participation involved an unmanned RAF Reaper drone.
The US, which brokered the truce with Russia, said it is making efforts to extend the agreement.
