Air raids on rebel-held districts of Syria's battleground second city of Aleppo killed 19 civilians including children on Saturday, a monitor said. 

"Eleven civilians, including four children, were killed by air raids after midnight in the Bab al-Nasr area of Old Aleppo, and seven others were killed in Fardous neighbourhood," the Syrian Observatory for Human Rights said. 

Another young girl was killed in the Maadi district, the Britain-based monitor said. 

The Observatory, which relies on a network of sources across Syria for its information, warned that the toll could rise due to the number of critically wounded. 

An AFP correspondent at the scene said helicopters and fighter jets were still circling rebel-held neighbourhoods, adding that barrel bombs -- crude, unguided explosive devices -- had been dropped on several areas. 

At least one barrel bomb struck just outside the hospital in the Maadi neighbourhood, the correspondent said. 

The Observatory said rebel fighters shelled government-controlled western areas of Aleppo, but had no immediate word on any casualties. 

Aleppo city is divided roughly between government control in the west and rebel control in the east.

A ceasefire brokered by Russia and the United States in February between government forces and non-jihadist rebels does not cover Al-Qaeda affiliate Al-Nusra Front which has a strong presence in many rebel-held areas.

The truce has been routinely violated, particularly in and around Aleppo. 

Last week, government forces advanced to within firing range of the last remaining supply route into rebel-held areas of the city, prompting food shortages and spiralling prices.

According to the United Nations, nearly 600,000 people are living under siege across Syria, most of them surrounded by government forces although rebel groups also use the brutal tactic. 

More than 280,000 people have been killed and millions have been forced to flee their homes since the Syrian conflict broke out in March 2011.

Source: AFP