Up to 5,000 Europeans have returned to the continent after being trained at terrorist camps, the head of Europol has reportedly said.
Rob Wainwright claimed Europe is facing its biggest terror threat in more than 10 years and has warned of large-scale attacks by IS and other groups.
The head of the EU law enforcement agency said: “The growing number of foreign fighters presents the EU countries with completely new challenges.”
At least 700 people from the UK have travelled to support or fight for jihadist groups in Syria and Iraq, according to police, and about half have since returned.
Read more: Sky News