© Reuters
Children returning from war zones controlled by Islamic State (IS, formerly ISIS/ISIL) in Syria and Iraq could grow up to be a new generation of jihadists, the chief of German intelligence has warned.

Some 950 people from Germany have left to join IS, 150 of whom have died, according to the Office for the Protection of the Constitution (BfV). However, as the militants rapidly lose ground across the Middle East, women and children - who make up around 25 percent of this group - are expected to flee, creating a new security risk, the BfV chief said on Wednesday.

"We see the danger of children who socialized with and were indoctrinated by jihadists returning to Germany from the war zones," said Hans-Georg Maassen. "This could allow a new generation of jihadists to be raised here."

IS is known to make use of children in its propaganda, showing videos of minors being trained to be jihadist fighters as well as carrying out executions. A number of these children were brought over by their parents to live in the terrorist group's self-styled caliphate.

Despite this, Maassen said there was a lack of a clear, unified strategy between security services, family courts and child protection agencies. The BfV chief added that members of the public need to "take a very serious look" at the threat, and call their hotline if they see anything suspicious. The BfV is also reaching out to refugees, from whom the agency has received hundreds of tip-offs.

"We operate on the assumption that many of these tips are real and thus worth us following them up," Maassen reported.

In June, Bavarian Interior Minister Joachim Herrmann called for increased powers for intelligence agencies to fight terrorism, including placing minors and children linked to Islamists under surveillance nationwide.

"In Bavaria, we have abolished the age limit for surveillance," he said. "Normally, the domestic intelligence agency in Bavaria would not place children under surveillance. But if there is concrete evidence that a 12-year old is with an Islamist group, we have to be able to monitor them, too."

"I would strongly urge that the age limit for surveillance [carried out by the BfV] be lowered throughout Germany."

Herrmann and Maassen's warnings come after a number of terrorist attacks carried out by minors in Germany. In July of last year, a 17-year-old Afghan refugee wounded five train passengers with an axe before being shot dead by police. Responsibility for the attack was claimed by IS.

In December, a 12-year-old boy of Iraqi origin tried to detonate a home-made bomb at a Christmas market in Ludwigshafen, western Germany.

The age of criminal responsibility in Germany is 14. Those under the age of 21 may face shorter and milder sentences for their crimes.