Boys and girls are being recruited in record numbers to act as soldiers, spies and sex slaves in Congo and children have been spotted marching in formation in the war-wracked east of the country over the past week, international charity Save the Children said Monday.

Fighting in lawless eastern Congo has escalated dramatically since August as rival rebel militias clash over the forested territory, the London-based charity said. Those children who have managed to escape have told the aid organization they were held captive in small holes in the ground.

“The situation for children in eastern Democratic Republic of Congo is catastrophic. Fighters from all sides are using children as frontline fodder,” said Hussein Mursal, Congo director for Save the Children.

Schools have been targeted as “rich recruitment ground,” the charity said.