Fifteen people, among them eight children, were killed in air raids Sunday on a rebel area of the war-torn northern city of Aleppo, the Syrian Observatory for Human Rights said.
The Britain-based Observatory also reported that at least 28 people have been killed in Adra, northeast of Damascus, since rebels launched an offensive there Wednesday.
"Fifteen people, including six men, an 18-year-old and eight children were killed in an aerial bombardment of the Ard al-Hamra neighbourhood" of Aleppo, it said.
The Aleppo Media Centre, an activist network on the ground, reported several helicopter attacks on rebel areas of the city, once Syria's economic hub.
The helicopters, said the group, dropped explosive-laden barrels on several neighbourhoods, causing widespread destruction.
Also in Aleppo, the Syrian Red Crescent on Saturday delivered food and medicine to the central prison, which has been under rebel siege for eight months.
The volunteers escorted out 15 prisoners, said the Observatory, adding that "another 341 detainees are waiting to be released."
President Bashar al-Assad's regime earlier this week announced an amnesty for scores of detainees at the jail "because of the poor health and humanitarian conditions," according to the Observatory.
Meanwhile, northeast of Damascus, at least 28 civilian members of minority religious communities have been confirmed dead in Adra since Wednesday, when Islamist rebels launched an offensive aimed at capturing the key entrance into the capital.
"The number of civilian fatalities has risen to 28... among them Alawites, Shiites and Druze," said the Observatory, which relies on a broad network of doctors, activists and lawyers across Syria for its reports.
The army has vowed to "crush" Islamist rebels in the industrial town, which has seen fierce fighting for five days.
Most of the country's Alawites -- whose religion is an offshoot of Shiite Islam -- support co-religionist Assad, and many members of other minority groups fear a Sunni Islamist victory in the Syrian conflict.
More than 126,000 people have been killed in Syria since March 2011, and millions more have fled their homes.