Returning Islamic State fighters pose a threat to their countries of origin, including Western Balkan states, says a new report from an NGO dealing with global security issues.

Of around 900 people from the Western Balkans who have gone to fight in Syria or Iraq, some 250 have returned to their home countries, according to a report published on Tuesday by the Soufan Centre, a US-based NGO dedicated to increasing awareness of global security issues.