A damaged classroom is pictured after an airstrikes in Syria.

At least 33 people were killed in a US-led coalition strike on a school used as a center for displaced people near a militant-held Syrian town, a monitor said Wednesday.

The Syrian Observatory for Human Rights said the strike south of Al-Mansoura, a town held by ISIS in the northern province of Raqqa, “took place in the early hours of Tuesday.”

The US-led coalition has been bombing ISIS since 2014 and is now backing a major offensive to defeat the group in Raqqa city, the Syrian heart of ISIS. The school-turned-shelter hit on Tuesday morning lies about 30 kilometers west of Raqqa.

“We can now confirm that 33 people were killed, and they were displaced civilians from Raqa, Aleppo and Homs,” said Observatory head Rami Abdel Rahman. “They’re still pulling bodies out of the rubble until now. Only two people were pulled out alive,” Abdel Rahman told AFP.

The Britain-based monitor says it determines what planes carried out raids according to their type, location, flight patterns and the munitions involved. “Raqqa is Being Slaughtered Silently,” an activist group that publishes news from ISIS-held territory in Syria, also reported the strike.

“The school that was targeted hosts nearly 50 displaced families,” it said. Syrian state news agency SANA also reported the air raid, accusing the US-led coalition of inflicting “dozens” of casualties and almost completely destroying the school site.

Earlier this month, the coalition said its raids in Syria and Iraq and unintentionally killed at least 220 civilians. But other monitors say the number is far higher. Trump has ordered his top generals to craft an accelerated strategy to “eradicate” ISIS’s so-called caliphate, and allied countries are keen to learn more at Wednesday’s meeting.

Syrian city of Raqqa, Daesh’s de facto captial.