The United Nations has suspended all aid convoy movements in Syria after an air strike hit a 31-truck convoy late on Monday, killing as many as 12 people.

On Tuesday, UN humanitarian aid spokesman Jens Laerke said the agency had recently been allowed by the Syrian government to deliver aid to all besieged areas in the country.

However, following the strike, all movements were suspended "as an immediate security measure".

David Swanson, a spokesman from the UN Office for the Co-ordination of Humanitarian Aid (UNOCHA), told the BBC the airstrike was a "devastating blow" for the Syrian people.

"As a result of the situation and the attack last night, we had no choice but to temporarily suspend the aid convoys that we had planned for the rest of this week," he said.

"We're still getting information and details as they're coming in, but what we are fully aware of is there was an attack on the aid convoy to a place called Big Orem. Of the 31 trucks that were involved in the convoy, which was carrying lifesaving assistance for some 78,000 people, 18 of them were hit by this strike. This is obviously a serious setback for the humanitarian community. We're waiting word on how best to proceed."

Mr Swanson could not confirm how many people died, but confirmed some of the dead were from Syrian volunteer group Red Crescent.

He branded the attack "absolutely obscene" and said it may have been a war crime.

"Obviously any attack on a humanitarian community or a humanitarian convoy is absolutely obscene and it doesn't make any sense to us," he said. "If it is deemed to be a deliberate attack, then obviously it could well prove to be a war crime."

Convoys which have been halted this week include 40 much-needed shipments which were headed to help hundreds of thousands of people in east Aleppo.

Those convoys are waiting at the customs point on the border with Turkey, Mr Swanson said, where they have remained for a week.

Two inter-agency humanitarian convoys were sent out in Syria on Monday. One managed to reach its destination in Homs, delivering aid to 80,000 people.

The other was hit by the air strike.

with Reuters