At least 80 people were killed and hundreds were injured in an airstrike carried out by the Syrian government under President Bashar al-Assad on Sunday. The target was a busy market place in Douma, located 10 kilometres from Damascus.
UK-based Observatory and the local arm of the Syrian Civil Defence said at least 80 people were killed and more than 200 were injured.
"This is a documented massacre," said Rami Abdulrahman of SOHR.
The Syrian military sources claimed that the air force carried out the attacks in Douma and the nearby area of Harasta to destroy headquarters of the rebel group, Islam Army.
The SOHR report noted that the Syrian Air Force fired at least 10 missiles during the attack. They allegedly continued to attack the town even after rescue workers arrived at the scene, SOHR added.
The retaliatory attack launched by the Syrian forces has come just a day after Islam Army militants attack Assad soldiers in Harasta.