An international aid convoy has been hit by an air strike while delivering aid to the hard-to-reach town of Urm al-Kubra in Syria.

At least 18 of the 31 vehicles were struck as they were delivering assistance for 78,000 people in the rebel-held town.

One report said at least 12 people were killed, most of them drivers.

Aid deliveries to besieged areas were a key part of the cessation of hostilities deal brokered by the US and Russia seven days ago.

However earlier the Syrian military announced in a statement that the effect of that “truce regime” which came into force on September 12 was now at an end.

Speaking in reaction to the announcement, US Secretary of State John Kerry said: “The important thing is the Russians need to control Assad, who evidently is indiscriminately bombing, including of humanitarian convoys. So let’s wait and see and collect the facts. We need to see where we are, and then we’ll make a judgment.”