Munich, Germany (CNN) The head of Britain's MI6 intelligence agency has warned of a resurgence of al Qaeda in Syria's ungoverned areas.

In a rare on-the-record meeting with journalists on the sidelines of the Munich Security Conference, Alex Younger, known as "C" or Chief in Britain's foreign intelligence service, also warned that even as ISIS nears territorial defeat in Syria, the terror group has "managed to morph and reconstitute ... in a more traditional, asymmetric threat."

Younger separately said the Idlib region of northern Syria, where al Qaeda affiliates have many Europeans in their ranks, "is increasingly radicalized and so there certainly exist people who we are very concerned about." He declined to say how many British citizens were there.

"We need to think about what happens when people in Idlib disperse and it's a pretty similar conversation" to how returnees from ISIS's so-called former caliphate are treated, he said. "These organizations exploit political failure essentially. They exploit ungoverned space to organize and grow."

Younger expressed concern that ISIS and al Qaeda could exploit "new technologies and [we must] make sure we are kind of ahead of them on all of them." He added MI6 needed to be "able to penetrate those terrorist organizations -- notwithstanding the fact that they are in some of the most forbidding places in the world -- and we do."

Read More