Children as young as thirteen have left Germany for the Middle East to wage jihad on behalf of the Islamic State, according to Hans-Georg Maaben, the head of Germany’s Federal Office for the Protection of the Constitution (BfV). “The youngest was 13,” he said in an interview with the Rheinische Post.

Maaben, the president of Germany’s equivalent to the FBI, estimates that at least twenty-four children have left their homes in the Deutschland for Syria and Iraq, and among them, five have returned with combat experience. Additionally, as many as four girls left for the Middle East with a “romantic ideal of marrying a jihadist” whom they had met online. “The vast majority are from migration backgrounds,” added Maaben.

Maaben added that foreign intelligence services and the kids’ parents have helped the BfV locate and track the large swath of child jihadis making their way in and out of Germany.

Some 400 German citizens have joined the Islamic holy wars in Iraq and Syria, according to security source estimates given to The Local.de. Of the 400-plus who initially left, about 130 have returned to their nation of origin, and another 40 or more have died on the battlefield. A study by Germany’s BfV found that the vast majority of the jihadis are poorly educated Muslim men who originated from foreign lands.

German Foreign Minister Frank-Walter Steinmeier said on Sunday that his country will not participate in any air strikes, nor will it get involved on the ground to support U.S.-led coalition efforts against the Islamic State fighters in Iraq and Syria.

Steinmeier asserted, “For us there is no question of it,” rejecting the possibility of Berlin getting further involved militarily. The German Foreign Minister said that measures to gain approval for arming the Kurds in Iraq “were not taken easily.” He added, “The alliance that has been formed is going to divide up the work. We have taken our part … of the responsibility.”

In late August, Germany announced that it was sending weapons to the Kurds in northern Iraq to help them stave off the advances of the Islamic State. Berlin also sent forty military advisers to help train the Kurdish Peshmerga forces.