Russian and Syrian Government aircraft have killed dozens of civilians in previous airstrikes on Douma
A teacher and two children were killed when a school was hit by unidentified warplanes in Syria, a monitoring group has said.
The Syrian Observatory for Human Rights said the school in rebel-held Douma was struck but it was not clear whether Syrian or Russian planes were responsible.
"One of the airstrikes on Douma hit near a school, killing the school's principal," said Observatory head Abdel Rahman.
Witnesses saw men carrying children across the dust-covered rubble of destroyed buildings in the town.
Suspected Russian strikes on Douma in November killed 23 Syrian civilians.
The Observatory said a total of 31 civilians died in insurgent strongholds east of Damascus on Sunday.
Some of these were killed by air-to-air missiles fired by Syrian forces, the monitoring group added.
But the Syrian army said its strikes target insurgents who have attacked its areas.
For their part, rebels reportedly killed at least three civilians, including a child, during mortar fire into government-held parts of Damascus.
Dozens more were wounded, state news outlets reported.