Nearly 200 people who joined extremist groups in Syria and Iraq as well as at least 175 children have ties to the Netherlands and are still in the strife-torn countries, mostly with the "Islamic State of Iraq and Syria" (ISIS), AFP reported Tuesday (March 6th).

"More than half of the minors are younger than four years, with at least two-thirds having been born on the battlefront," the Dutch intelligence and security agency AIVD said in its 2017 annual report.

Of around 280 people who have left the Netherlands since the start of Syria's civil war in 2011 to join extremist groups, about 185 were still in the region, said the AIVD, also warning that an increasing number of them were coming back home.

"We are expecting more returnees, mainly women and children, now that ISIS has lost almost all of its territory," the Dutch agency said.

"The returnees form a serious threat because they were in the (ISIS) area for a long time. Most likely they took part in, or witnessed serious acts of violence, including the children," the AIVD said, believing they had become "ideologically more hardened."

Around 50 people have returned from extremist-held areas in Syria and Iraq since 2011, a third of them women, the agency said recently.