Fresh airstrikes were launched in northern Syria's Aleppo province Tuesday, hours after 18 trucks in a UN humanitarian aid convoy were hit in an attack in the area that could amount to a "war crime," according to the top UN official.
Fresh fighting also took place between ground forces in the northern province, according to the Britain-based Syrian Observatory for Human Rights.
The US said it was still unclear if it was a Russian or a Syrian plane that hit the 31-truck UN aid convoy late Monday, but officials placed the blame on Moscow, a key ally of Syrian President Bashar al-Assad.
The new wave of bloodshed comes after al-Assad's army declared the end of a week-long truce brokered by the US and Moscow. The government and the rebels traded blame over the collapse, accusing the other side of hundreds of breaches.
"If this callous attack is found to be a deliberate targeting of humanitarians, it would amount to a war crime," said Stephen O'Brien, the top UN humanitarian official, adding that the warring parties had been told about the aid convoy.
The Syrian Arab Red Crescent was also hit during Monday's strike, as was a warehouse run by the group. SARC volunteers were among the more than 35 killed in the first hours after violence resumed following the formal end of the truce.
The rebel-held east of Aleppo city, with hundreds of thousands of residents, has been cut off from aid deliveries since July despite the ceasefire, making the situation at hospitals treating the wounded more complicated due to shortages.