Disturbing imagery circulated quickly on social media, initially distributed by Iranian state media and republished by news services. USA TODAY is not publishing many of those images because of the graphic nature of the content.

They show destroyed classrooms, bloodied backpacks and colorful school materials strewn across the site. Dust covering every surface. The remains of a playground, including a slide, were scattered amid mounds of concrete rubble. Children's bodies could be seen partly buried under the debris.

One video shot by a bystander shows a chaotic scene with fires from the apparent airstrike burning on the adjacent property. Moments later they pan to the right to reveal the school filled with smoke.

Iranian authorities said the strike killed up to 175 people, most of them elementary-school-aged girls. It may be the deadliest known mass casualty event involving civilians of the war so far, though USA TODAY could not independently verify many details about the incident including the exact death toll, the identities of those involved and who was responsible for the strike.

The adjacent facilities appeared to be linked to an Islamic Revolutionary Guards Corp naval base at some point, according to Farzin Nadimi, a Washington, D.C.-based analyst at The Washington Institute who specializes in the security and defense affairs of Iran and the Persian Gulf region.