The UN suspended all humanitarian convoys in Syria on Tuesday (September 20th) following a deadly airstrike on aid trucks, AFP reported.

The Monday strike on an aid convoy heading for Aleppo killed "around 20 civilians" including an employee of the Syrian Red Crescent, the International Federation of Red Cross and Red Crescent Societies (IFRC) said.

The incident provoked outrage from UN officials, with aid chief Stephen O'Brien warning that if deliberate "it would amount to a war crime".

The IFRC said at least 18 of 31 vehicles had been destroyed, along with a Red Crescent warehouse in Orum al-Kubra in Aleppo.

"Much of the aid was destroyed," the IFRC said, noting that "the attack deprives thousands of civilians of much-needed food and medical assistance".

Omar Barakat, who headed the local Red Crescent branch, was wounded in the strike and later died, IFRC spokesman Benoit Carpentier said.

UN humanitarian agency OCHA said that the movements of all aid convoys in Syria had been suspended as an "immediate security measure".

The attack marked a "very, very dark day for humanitarians in Syria and indeed across the world", OCHA spokesman Jens Laerke said, adding that it is "paramount that we are able to establish the facts through an independent investigation".

The strike came just hours after the Syrian regime announced the end of the truce.