At least 11 people, including a rebel chief, have been killed after government airstrikes battered an opposition-held district in the northern Syrian city of Aleppo, local sources told Al Jazeera.

Nabhan Satuf, a leader of the Ahrar al-Sham (Liberation of Damascus) rebel group, was among those killed in the attack on Andan on Sunday, the sources said.

Activists said there was an increase in raids by government warplanes in Aleppo's rebel-controlled outskirts in retaliation for recent attacks on the predominantly Shia villages of Nubul and Zahraa.

The heightened violence came as a woman and her three sons were killed in the government-held side of Aleppo city by rebel-fire, the Syrian Observatory for Human Rights said.

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The woman and her children were killed when a homemade rocket fired from the rebel-held east of the city hit their home in Ashrafiyah district.

The UK-based rights group said fighters were firing homemade explosive devices often using gas canisters that were more damaging than regular mortar fire.

Aleppo, Syria's second city and former industrial powerhouse, has been divided between rebel control in the east and government control in the west since fighting began there in 2012.

Since 2013, the Syrian air force has regularly dropped explosive-packed barrel bomb, which rights groups criticise as indiscriminate, on the rebel-held east and areas surrounding the province.

The barrel bomb attacks have killed several thousand people in Aleppo province, according to the Observatory.

In recent months, rebels have intensified their mortar attacks on the government-held west of the city, killing nearly 300 people in four months, the group said.

Source: Al Jazeera and agencies