The victims reportedly included a two-month-old baby and a three-year-old girl.

The Syrian Observatory for Human Rights monitor said that 15 civilians, among them 11 children, were killed in the attack on the Bab al-Nayrab neighborhood in the south of Aleppo.

The attack comes as Russia - which has been backing Assad in the civil war - agreed to a 48-hour humanitarian ceasefire in the city on Thursday night. Jan Egeland, who chairs the UN task force, reportedly said getting the go-ahead from all sides "has taken more time frankly than I thought was needed."

An international team recently blamed the Assad government of using chlorine gas in two attacks.

US State Department spokesman Elizabeth Trudeau, meanwhile, said the US would support the UN but added: "Our focus is on a nationwide sustainable cessation of hostilities."

Meanwhile, a ceasefire has been agreed in the town of Daraya, allowing 700 rebel gunmen safe passage to the northern province of Idlib and allowing 4,000 women and children to escape to shelters outside the town. Daraya is south-west of Damascus and has been blockaded by government forces for nearly four years.

Syria's regime has been accused of regularly using barrel bombs on rebel-held areas that are home to civilians.

Other parties to the conflict are not known to have used the weapons.

Assad and his government deny using barrel bombs.

Aleppo has been ravaged by the conflict that began with anti-government protests in March 2011. It has been roughly divided between rebel control in the east and government control in the west since mid-2012. Around 250,000 people live in the city's eastern districts, while another 1.2 million live in its western neighborhoods.

Fighting for the city intensified after regime troops seized control of the last supply route into rebel-held areas in mid-July.

More than 290,000 people have been killed in Syria since the conflict began, according to the Observatory.

jbh/kl (AFP, Sky News)