A government air strike on a marketplace in the rebel-held town of Douma killed at least 80 people on Sunday, according to the BBC. About 200 other people were reportedly injured in the attack.
The attack by the Syrian government occurred 15 kilometers (10 miles) from the city of Damascus, according to the Huffington Post. Syrian military sources report that the air strikes carried out were targeting the headquarters of the rebel group Islam Army.
This attack was one of the deadliest attacks in the country's war, according to the AFP. The head of the Syrian Opposition National Coalition, Khaled Khoja, called Sunday's attack a "massacre" that "will not go unpunished," according to the AFP.
The Syrian Observatory for Human Rights reported at least 10 strikes occurring in the Douma area, according to the AFP. Most of the air strikes hit the marketplace, while others hit nearby in the center of the town.
Of the reported 10 strikes, several are reported to have stuck Douma after rescue workers had arrived, according to the Huffington Post.
This Sunday's air strikes fall in line with the first visit by Stephen O'Brien, the U.N. humanitarian chief, since he took the position in May, according to the BBC.
Since it began four years ago, U.N. estimates show that over 220,000 people have been killed in Syria's civil war, according to the BBC.
