A number of airstrikes were carried out Monday in rebel-held eastern Aleppo, hours after Syrian army declared the end of a ceasefire sponsered by the US and Russia, according to activists and a monitoring group.
The raids, which also hit the outskirts of the city, resulted in an unidentified number of deaths and injuries, according to the Britain-based Observatory for Human Rights.
There were reports, including by the Observatory, that aid trucks were hit by fire, though the details were unclear. Aid agencies, including the Syrian Red Crescent (SARC), had earlier said they were carrying out deliveries in the Aleppo countryside.
"Unfortunately, we have received a devastating news about one of the SARC structures in rural Aleppo coming under attack," said Ingy Sedky, a spokeswoman for the International Committee of the Red Cross.
“The situation on the spot is very chaotic and we are deeply shocked that humanitarian workers and missions have yet again suffered from the brutality of this conflict."
Rebel held eastern Aleppo has been cut off from aid deliveries since July, despite the ceasefire. Ibrahim al hajj, a member of the White Helmets, a rescue group operating in rebel held areas, told dpa there had been a large number of airstrikes.
"Our hospitals are lacking essential first aid supplies. Simple thing like bandages are lacking," he said by telephone from eastern Aleppo. "The situation inside hospital is miserable."
Syria's government and key rebel forces traded blame for the collapse of the ceasefire, which attempted to reduce violence and increase aid flows.
"It was a real chance to stop the bloodshed, but the armed terrorist groups flouted this agreement and failed to comply with the application of any provision of its clauses," the army statement said, alleging rebels breached the deal 300 times.
Mohammed Alloush, a former top negotiator and a member of the Islam Army (Jaish al Islam) rebel group, blamed the government, claiming "this regime has violated the ceasefire more than 250 times."
An airstrike on a Syrian army post in the east of the country on Saturday by the US-led anti-Islamic State coalition killed more than 60 Syrian soldiers, further complicating the ceasefire.
Syrian President Bashar al-Assad slammed "blatant American aggression."
The US and its allies have expressed regret for the incident, with Washington saying Islamic State was the target of the airstrike and that it had informed Russia.
Extremists are fighting alongside rebels against al-Assad because the opposition relies on the strength of hardline groups. Analysts suggest it will be hard to disentangle the factions.
Ahead of the Syrian army announcement, Russia accused the rebels of violating the deal.
Moscow also expressed anger that Washington failed to separate so-called moderate opposition members from United Nations-designated terrorists, including al-Qaeda-linked militants.
"Militants are not observing the ceasefire. We believe that its unilateral observance by Syrian government forces is meaningless," Russian General Sergei Rudskoi said in comments carried by state news agency TASS.
Some 40 trucks ready to transfer aid assistance to eastern Aleppo, where 300,000 people are living under siege, are still stuck at the Turkish border waiting for permission from the Syrian government.
The US-Russian agreement for a ceasefire in Syria stipulated that it was to last for seven days and, if successful, the two countries would consider carrying out joint strikes against targets such as al-Qaeda-linked fighters.
The US on Monday asked Russia to confirm whether it will continue to adhere to the ceasefire in Syria.
"While we have seen comments attributed to the Syrian military, our arrangement is with Russia, which is responsible for the Syrian regime's compliance, so we expect Russia to clarify their position," State Department spokesman John Kirby said in Washington.
Turkish President Recep Tayyip Erdogan, a key backer of the armed opposition in northern Syria, earlier in the day repeated his call for a no-fly zone in the north.
This call has already been rejected by policy makers in Washington as too difficult to implement, especially since Russia began an air campaign last year.
However, Turkey recently sent troops into northern Syria to take territory from Islamic State and also from the Kurds, though the US has convinced Ankara to refrain from further attacks on Washington's Kurdish allies.
This means Turkey controls territory it could turn into a safe zone, though analysts warn Ankara it would need to continue to commit thousands of troops to Syria for a lengthy period.