Hundreds of killer kids known as ISIS “Caliphate Cubs” have been wiped out in the fierce battle over Mosul in Iraq, a British watchdog group said Monday.

More than 300 of the tiny terrors have been killed since Oct. 17 when Iraqi security forces moved in to liberate the city from the savage terrorist group, according to the Syrian Observatory for Human Rights.

In the last 24 hours alone, the corpses of 40 Islamic State soldiers were discovered in Mosul — and most of the dead were members of the “Caliphate Cubs.”

Meanwhile, the Islamic State appeared to be losing ground fast in Iraq’s second-largest city as government forces have already reclaimed many villages.

As a result, ISIS has resorted to desperate measures, slaughtering more than 250 civilians and herding together thousands more to use as human shields to try to hold on to the city.