ALEPPO • Air raids and shelling pounded key battle fronts in Syria yesterday, as outrage mounted over a strike on an aid convoy hours after Syria's military declared an end to a week-long truce.

The United Nations said it was suspending all humanitarian aid convoys in Syria after the deadly raid late on Monday, which killed several civilians including a senior employee of the Syrian Red Crescent.

The strike and renewed violence across the country dimmed hopes that the fraught ceasefire negotiated by Moscow and Washington could be revived.

The Russian Defence Ministry rejected assertions yesterday that the aid convoy had been shelled or struck from the air, saying it had caught fire instead.

"We have studied video footage from the scene from so-called 'activists' in detail and did not find any evidence that the convoy had been struck by ordnance," ministry spokesman Igor Konashenkov said in a statement. "There are no craters and the exterior of the vehicles do not have the kind of damage consistent with blasts caused by bombs dropped from the air."

He said damage to the convoy visible in footage was instead the result of its cargo catching fire, which had "oddly" occurred at the same time as militants had started a big offensive in nearby Aleppo.

Russia had stopped monitoring the convoy after it had delivered its aid, after which its whereabouts had been known only to militants on the ground, he added.

Monday night's raid on the convoy destroyed at least 18 of 31 vehicles delivering aid under a joint UN, Red Cross and Red Crescent operation for the town of Orum al-Kubra in Aleppo province.

The Syrian Observatory for Human Rights (SOHR), a Britain-based group, said 12 Red Crescent volunteers and drivers died in the strike.

Mr Jens Laerke, a spokesman for the UN humanitarian agency, told reporters in Geneva that as an "immediate security measure, other convoy movements have been suspended" following the raid.

This marks a "very, very dark day for humanitarians in Syria and across the world", he said, stressing that it was "paramount that we are able to establish the facts through an independent investigation".

Russia is flying a bombing campaign in Syria in support of Syrian President Bashar al-Assad and there are suspicions that either Moscow or the Syrian forces it supports are responsible for the strike.

Aid to desperate civilians was a key element of the United States- Russia deal, but deliveries were minimal during the truce and cross-border assistance for besieged civilians in the eastern parts of Aleppo city never entered Syrian territory.

Yesterday, US Secretary of State John Kerry insisted that hopes for a ceasefire in Syria remain alive after meeting officials of Russia and key powers with a stake in the civil war.

"The ceasefire is not dead," he insisted, one day after the Syrian military declared a week-old truce over and launched new bombardments on rebel-held cities.

UN envoy Staffan de Mistura confirmed there was still hope of reviving the ceasefire, but admitted that delegates agreed it was in danger.

The 23-nation International Syria Support Group, chaired by Mr Kerry and Russian Foreign Minister Sergei Lavrov, met in New York on the sidelines of the UN General Assembly. The talks were brief and, participants said, tense.

"The mood is that nobody wants to give this thing up," British Foreign Secretary Boris Johnson told reporters. "Quite frankly, the Kerry- Lavrov process is the only show in town and we've got to get that show back on the road."

At least 39 civilians were killed in overnight bombardment of Aleppo and the surrounding province, the SOHR said, and fresh clashes erupted on the city's southern edges.

In the week after the truce was declared on Sept 12, only 27 civilians were killed as fighting dropped significantly across the country.

AGENCE FRANCE-PRESSE, REUTERS