A video posted online by the Islamic State-linked Amaq News Agency on Thursday appears to show the aftermath of an airstrike that killed an unknown number  of civilians, including several children, in the Iraqi city of Mosul.

In the video, Amaq said the bombed site was a refugee shelter in the Hay al-Fatah neighborhood of Mosul. One unidentified man, speaking to the camera,  described the bombed-out facility as a school. “We don’t say it was hit by accident — it was intentional,” he said.

The damage to the structures in the video appears consistent with an airstrike or ground-based rocket artillery, though it is unclear how recent the video is or where exactly it was filmed. The footage shows dead children being pulled from the rubble, while others appear to be in critical condition.

Maj. Adrian Rankine-Galloway, a Pentagon spokesman, said in an email that the U.S. military was aware of the video.

“As we do with all reports, we will look into this allegation,” he said.

It is unclear how many civilians were killed in the alleged strike. Some reports on social media put the death toll between 20 and 80.

The reported strike comes as Iraqi forces, backed by U.S. troops and aircraft, began a renewed push into western Mosul after weeks of relative calm. While Iraqi forces have cleared the eastern reaches of the city, the western portion — with its cramped alleyways and side streets — has proved nearly insurmountable for advancing troops. The new advance, led by armored units and ground troops, is approaching from a different direction in an effort to break the stalemate before the Muslim holy month of Ramadan.

In March, a U.S. airstrike on a building in Mosul looks to have been at least partially responsible for the deaths of dozens of civilians. U.S. military officials have acknowledged having some role in the strike, though the Pentagon is still investigating other possible causes.

To date, the U.S.-led coalition has acknowledged  killing 352 civilians during its nearly three-year-old air campaign over Iraq and Syria. That figure, according to some monitoring groups, is extremely conservative. The group Airwars estimates that U.S.-led airstrikes have killed more than 3,000 civilians in both countries.