All aid convoys in Syria have been suspended after an attack on 18 trucks carrying humanitarian supplies killed 20 people.

United Nations spokesman Jens Laerke said Syria's security situation was being reviewed, adding it had been a "very dark day" for aid agencies around the world.

The convoy operated by the Syrian Arab Red Crescent (SARC) was attacked in rebel-held Urm al Kubra near Aleppo on Monday night.

Image: A damaged truck carrying aid in the town of Orum al-Kubra

Witness Mohammed Rasoul said the fleet had been "erased from the face of the earth".

The attack happened hours after a US-led airstrike killed 60 Syrian soldiers at the weekend. America apologised for the bombing, which occurred on a base near Deir al Zor airport, insisting that its intended target was Islamic State fighters.


Britain admitted playing a role in that strike but the Ministry of Defence insisted it would never "intentionally" strike Syrian forces.

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The US has expressed outrage at Monday's convoy attack which officials said could only have been carried out by the Syrian regime or Russia.

"The destination of this convoy was known to the Syrian regime and the Russian Federation," said State Department spokesman John Kirby.

But a Russian ministry spokesman has suggested the attack could only have been the work of militants because "all information on the whereabouts of the convoy was available only to the militants controlling these areas".

UN aid chief Stephen O'Brien called for an investigation warning that the "callous" attack could amount to a war crime if it found to have been deliberate.

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Image: SARC worker Omar Barakat was killed in the convoy attack