An airstrike believed to have been carried out by the U.S.-led coalition against ISIS killed 15 people, including four children, in a village west of the jihadists' stronghold of Raqqa on Saturday, the Syrian Observatory for Human Rights said.

The spokesman for the U.S.-led coalition could not be reached for immediate comment.

The airstrike took place at Hanida, some 30 kilometers (20 miles) west of Raqqa on the southern bank of the Euphrates River, the Observatory said.

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Elsewhere in Syria, a pair of activist groups reported that a U.S.-led coalition airstrike hit a boat carrying civilians fleeing across the Euphrates River, killing seven members of the same family. The groups Raqqa is Being Slaughtered Silently and Sound and Picture reported that the attack killed a woman and her six children. The attack occurred in the Shuaib al-Zeker area near where U.S.-backed Syrian fighters have been on the offensive against IS under the cover of coalition airstrikes.

On Friday, the U.S. fired 59 Tomahawk missiles at Shayrat airbase outside of Homs, Syria, the first American attack on a Syrian government military base since the civil war began.

A pentagon spokesman said that the base was believed to be where the chemical weapons attack launched on Syrian citizens earlier this week originated. According to the spokesman the targets hit in the attack were "aircraft, hardened aircraft shelters, petroleum and logistical storage areas, ammunition supply bunkers, air defense systems and radars."

Syria called the operation "an aggression" while state TV reported nine civilians killed. Rebels welcomed the U.S. operation.

U.S. President Donald Trump said after his meeting with Chinese President Xi Jinping that the airstrikes were a national security interest of the United States. He called on "the civilized nations of the world" to join the U.S. in "ending the slaughter and bloodshed in Syria."