U.S.-led coalition warplanes struck a building used as a prison by the Daesh terrorist group, killing scores of people, including dozens of civilians, local sources told Anadolu Agency (AA) yesterday.

The coalition has continued to target the Hejjin district and surrounding towns and villages in Syria's eastern Deir ez-Zor province, much of which still remains under Daesh control.

According to local sources in Deir ez-Zor, coalition fighter jets early Wednesday targeted a building near the town of Siife in which Daesh terrorists had been holding a number of prisoners.

The airstrikes reportedly killed dozens of people, most of whom were civilians being forcefully held by the terrorist group.

The coalition was cobbled together in 2014 after Daesh overran vast swathes of territory in both Iraq and Syria.

The U.S.-backed People's Protection Units (YPG) terrorist organization, which is also a Syrian affiliate of the PKK, meanwhile, continues to occupy the eastern and western outskirts of Deir ez-Zor, which is located east of the Euphrates river.

Despite the fact that the group receives active support from the U.S. and France, it appears unable to clear the province of Daesh terrorists.

Following an assault in which an estimated 6,000 of its members participated, the YPG recently succeeded in capturing the town of Suse but was forced to withdraw shortly after.

The U.S.-led coalition has continued to target Deir ez-Zor's towns of Hejjin, Siife and Suse, along with the villages of Bu Hassan and Bu Hatr, all of which remain under Daesh control.

Syrian regime forces, meanwhile, remain deployed in the province's western regions.

While the YPG/PKK terrorists currently occupy some 28 percent of Syrian territory, Daesh is estimated to hold only 3 percent.

Deir ez-Zor is not the only province where coalition forces have killed civilians. In June, Amnesty International said the U.S.-led coalition's 2017 assault on Raqqa killed hundreds of civilians and reduced sections of the city to rubble.

Researchers for Amnesty International interviewed more than 100 residents and visited 42 coalition targets in the city in a two-week period in February. They published their findings in a report titled "'War of Annihilation': Devastating Toll on Civilians, Raqqa - Syria" in reference to the language used by U.S. Defense Secretary Jim Mattis in the lead-up to the campaign.

"When so many civilians are killed in attack after attack, something is clearly wrong," said Donatella Rovera, one of the researchers who visited the city.