Forces supporting Syrian President Bashar al Assad have been blamed for the attack
At least 13 people, mostly children, have been killed in the Syrian city of Aleppo after barrel bombs were dropped into a crowded residential area.
Activists and a doctor in the battered rebel-held part of the city blamed forces supporting the regime of Syrian President Bashar al Assad for the attack.
It comes as Russia - which has been backing Syria's President Bashar al Assad in the war - agreed to a 48-hour humanitarian ceasefire in the city on Thursday night.
Aleppo is a city divided between the rebel-held east and the regime-held western areas, where there are extreme food shortages and a desperate need for aid.
While Russia has backed the UN-proposed deal, other sides are yet to agree.
Jan Egeland, who chairs the UN task force said getting the go-ahead from all sides "has taken more time frankly than I thought was needed".
US State Department spokesman Elizabeth Trudeau said they would support the UN but added: "Our focus is on a nationwide sustainable cessation of hostilities".
A UN report has concluded the Syrian government and Islamic State used chemical weapons during attacks in Syria in 2014 and 2015.
An international team blamed the government of Bashar al Assad for using chlorine gas in two attacks.
Islamic State used mustard gas during another attack, the Organisation for the Prohibition of Chemical Weapons-United Nations Joint Investigative Mechanism (JIM) found.
Three other attacks appeared to have been carried out by the government but it could not be certain, the team said in its report.
Responding to the report, Foreign Secretary Boris Johnson said: "Chemical weapons inflict excruciating pain and suffering.
"The Assad regime's indiscriminate and sustained use of them against their own people, including children, is horrific and must stop. Those responsible must be held to account.
"The report also identifies Daesh as a perpetrator. The Global Coalition is making progress in defeating Daesh and the UK will continue to play a leading role."