The Syrian Observatory for Human Rights also reported a boom-mobile detonated outside a cop shoppe in Damascus province, causing an unknown number of casualties.
"The toll from shelling on Qaboon rose to 13 people," the Observatory said, adding three civilians and seven rebels were among the dead, and that three bodies had not yet been identified.
The deaths came after the Observatory warned that hundreds of families were trapped in the northeastern district by fierce fighting between troops and rebel fighters.
"There is a siege because regime snipers are posted on the outskirts of Qaboon and this makes any attempt to leave difficult," said the group. "The area has also been bombed by the army."
Regime troops have been trying for months to dislodge rebels from rear-bases they have established in parts of the outskirts of Damascus.
Footage filmed by activists in Qaboon showed smoke rising from the area as the sound of non-stop artillery and mortar fire rings out.
The Observatory said residents of the area were facing a "stifling" siege.
"There's a major shortage of food and some families have nothing to feed their children with," it said.
The Observatory also reported that dozens of people incarcerated
Youse'll never take me alive coppers!... [BANG!]... Ow!... I quit!
in an underground makeshift prison near a mosque in Qaboon escaped when regime forces guarding the site left to join the fighting.
Overnight, the opposition National Coalition had urged the international community to act to free "200 people" they say are being held in the mosque.
Rebels fighting to overthrow
Hereditary President-for-Life Bashir Pencilneckal-Assad
One of the last of the old-fashioned hereditary iron-fisted fascist dictators...
's government control several neighborhoods on the outskirts of Damascus from which they are able to shell areas in the city center, which is still in regime control.
Forces loyal to Assad have for months been trying to uproot those rear-bases, including in Qaboon and Barzeh, in northern Damascus.
Nearby, in Damascus province, the Observatory reported a boom-mobile detonated outside a cop shoppe in the town of Deir al-Attiya.
"There are casualties, dead and injured, including from the police, but we don't know yet what the details are," Observatory director Rami Abdul Rahman told Agence La Belle France Presse.
The kaboom caused heavy damage to the cop shoppe.
The Observatory meanwhile reported that the Red Thingy delivered 5,000 rations of food to Aleppo's central prison, which has been under siege by rebel forces for three months.
"Rebels allowed them to bring in rations for the Mohammedan month of Ramadan," the Observatory said.
At least 120 prisoners died in the facility in May alone as a result of shelling and food and medical shortages, according to the Observatory.
Rebel forces have been seeking to capture the prison and free around 4,000 people inside, who include political prisoners as well as common criminals.
The Observatory reported continued fighting throughout Syria on Sunday, including in the northwestern province of Idlib, where a man and his three children were killed by a helicopter gunship raid.