ERBIL, Kurdistan Region – Some 300 Syrian child soldiers brought in by ISIS to Iraq have been killed since the start of the Mosul offensive a fortnight ago, the Syrian Observatory for Human Rights said Sunday.

The UK-based watchdog said that the dead bodies of 40 ISIS militants killed in Mosul had arrived in the group’s de facto capital of Raqqa in Syria over the last 24 hours, the majority of them among the so-called children’s brigade, or “lion cubs of the caliphate.”

“This will raise the death toll to at least 480 Syrian fighters killed in the ranks of the Islamic State since the start of the battles in the Mosul area, among them more than 300 child soldiers from the ‘lion cubs of the caliphate,’” the Observatory said.

It added that the group’s preachers had told residents in Syria that the losses in Dabiq -- a symbolic town for ISIS which it lost to the Turkish-backed rebels earlier this month -- was compensated with victory in Mosul.

On Thursday, General Joseph Votel, head of the US Central Command, said that between 800 and 900 ISIS militants were killed since the beginning of the Mosul operation on October 17.