Rebel groups around Syria have scored victories in recent weeks, overrunning military bases and airports and halting air traffic at the capital's international airport for days.
The government's response has been harsh, and suburbs to the east and south of Damascus have seen some of the heaviest fighting since July, when rebels seized neighborhoods in the capital itself before being routed by government troops.
Death tolls in the area have soared. On Tuesday, reports emerged of at least four killings of at least a dozen people, all of them near Damascus or in Aleppo, Syria's largest city and a battleground since the summer.
Syria's state news agency SANA said nine students and one teacher were killed when a mortar fired by "terrorists" — the regime's shorthand for rebels — hit a ninth grade classroom in the Al-Wafideen area. The housing project, about 25 kilometers (15 miles) northeast of central Damascus, houses 25,000 people displaced from the Golan Heights since the 1967 war between Syria and Israel.
SANA said earlier that 29 students and one teacher had been killed before reporting the lower number.
The opposition Syrian Observatory for Human Rights said 10 were killed and did not specify who fired the mortar.
The Britain-based group, which relies on contacts inside Syria, also said 17 unidentified bodies were found in the southern Damascus suburb of Thiyabiyeh. An activist video posted online showed the dead lined up on a floor, many of their heads bloody. An off-camera voice said they were shot after being detained at government checkpoints.
The Observatory also said 12 others were killed in a shelling attack on the Aleppo neighborhood of Bustan al-Qasr the day before. Online videos showed bloody and dismembered bodies on a sidewalk as people struggled to lift the wounded
Nearby, dozens of men stood in what the unidentified cameraman said was a bread line.