31 Syrian soldiers were killed in bomb attack at a government building in a town on the outskirts of the capital, a monitoring group that documents Syrian battlefield developments said.
Head of the British-based Syrian Observatory for Human Rights Rami Abdelrahman, said that the building in Harastas completely levelled by the explosion.
Only the night staff were on duty when the explosion occurred.
If the bomb had gone off an hour before, there could have been up to 200 dead.
More than 100,000 people have been killed in a civil war that started two and a half years ago when forces loyal to President Bashar al-Assad opened fire on protests demanding an end to four decades of Assad family rule.
In recent weeks, the army and pro-Assad militia have taken ground in the north and opposition fighters have resorted to bomb attacks and mortar strikes into government-held territory,including the capital.
Harasta is mostly in government hands but rebels have been trying since summer 2012 to advance into it.