According to the Syrian Observatory for Human Rights (SOHR), US-led coalition warplanes reportedly carried out 17 air strikes after midnight on the de facto capital of ISIS in the northern Syrian province of Raqqa, killing and wounding dozens.
At least 15 ISIS members were killed while dozens of others were wounded, the Britain-based SOHR reported.
SOHR said that an aerial bombardment by a drone yesterday targeted a school in the Raqqa area, hitting a vehicle carrying an ISIS member and killing six civilians, including a man and his child son, while others were wounded.
The US-led coalition said they conducted “significant” air strikes against ISIS in Raqqa.
"The significant air strikes tonight were executed to deny Daesh (ISIS) the ability to move military capabilities throughout Syria and into Iraq," coalition spokesman Lieutenant Colonel Thomas Gilleran said.
"This was one of the largest deliberate engagements we have conducted to date in Syria and it will have debilitating effects on Daesh's ability to move from Raqqa."
Coalition forces "successfully engaged multiple targets" throughout Raqqa, the statement said, destroying ISIS structures and transit routes.
The strikes "have severely constricted terrorist freedom of movement," it added.
US-led coalition started its air strikes in Syria and Iraq last September targeting ISIS positions in Syria and Iraq, where the group has proclaimed the establishment of a state in territory under its control.
ISIS, which emerged in Syria in 2013, currently controls around 50 percent the country's territory, though much of the land it holds is unpopulated desert.
More than 220,000 Syrians have been killed so far in the country’s four-year civil war according to UN estimates. More than 6.7 million Syrians, 70 percent of the country's population, are displaced internally. While at least 5 millions have fled the country to neighbouring Turkey, Iraq, Lebanon and Jordan.