DAMASCUS, Syria — A car bomb near the Damascus headquarters of Syria’s ruling party killed 53 people and wounded more than 200 on Thursday, while a government airstrike on a rebel field hospital in southern Daraa left 18 dead, opposition activists and state media reported.

The Damascus car bomb was one of at least three attacks in the heart of the city. A second blast shook another neighborhood and mortar rounds exploded near the Syrian Army General Command.