The Britain-based Syrian Observatory for Human Rights says the attack on a busy market in Douma killed 58 and wounded more than 200.
A Douma-based activist who goes by the name of Mazen al-Shami said the air raids struck the main market today, adding that more than 60 have been killed.
Al-Shami said hundreds of people were in the busy market when the first missile struck the area, inflicting heavy casualties.
Syria's civil war, now in its 5th year, has killed more than 250,000 people and wounded at least a million.