The senior intelligence official, quoted by CNN, said at the Munich conference "With IS' retreat in the east of the Euphrates, al-Qaeda began to emerge in northwestern Syria."
In a rare meeting with reporters on the sidelines of the Munich Security Conference, Alex Junger warned that even as IS' regional defeat in Syria approached, "the terrorist group has been able to change and reshape itself to become more dangerous."
As for the city of Idlib, he said, "There are many Europeans in the ranks of al- Qaeda there, they are becoming more radical and therefore we are very concerned about what is happening there in northwestern Syria."
He refused to say how many British citizens there were.
He added, "We need to think deeply, especially after the elimination of IS caliphate, and as a result of the transformation of the latter, it is possible to go to areas like Idlib, especially since the latter is in a state of great chaos."