UN 'ready' to resume Syria aid after convoy attack

"The preparation for these convoys has now resumed and we are ready to deliver aid to besieged and hard-to-reach areas as soon as possible," the UN's humanitarian office (OCHA) said in a statement.

The Monday attacks came as relief supplies intended for desperate Syrian civilians were being unloaded at the warehouse Orum al-Kubra, a town in Aleppo province.

Those killed included volunteers as well as a Syrian Arab Red Crescent (SARC) staffer.

The UN announced it was suspending all deliveries on Tuesday morning and called for an investigation.

The Syrian Observatory for Human Rights, a UK-based monitor group, said the attack was the result of airstrikes, which if confirmed, would strongly implicate Russian or Syrian aircraft as neither opposition nor jihadist groups have air power.

An unnamed US official told AFP that Washington believed a Russian plane was responsible. US Secretary of State John Kerry on Wednesday also demanded that Russia ensure the grounding all Syrian war planes in order to "restore credibility". 

Both Moscow and Damascus have denied involvement.

	One of the 18 aid trucks destroyed on Monday [AFP]

A day after the attack, Russia alleged that the Syrian White Helmets rescue teams had some involvement in the incident.

According to the Russian defence ministry, the convoy "caught fire" after an attack by the al-Nusra front on Aleppo, adding that there was no evidence at the sight of an aerial attack.

Opposition groups have rejected this claim, pointing to footage of the attacks that include the sounds of what are believed to be war planes dropping bombs.

Images have also emerged of cratres in the earth that appear to have been caused by bombs from planes.

This dispute has heightened tensions the US and Russia - the nations that brokered Syria's latest ceasefire - and puts hopes of peace in further peril.

Boosting aid deliveries has become a top UN priority in Syria, with convoys repeatedly blocked for security reasons, refusals by the Syrian government to grant authorization and strict conditions imposed by opposition groups.

OCHA on Wednesday restated its call for "safe, unconditional, unimpeded and sustained access to all Syrians in need, wherever they are."