Glenn Audenaert, head of the federal police in Brussels, says that according to a study by the police and security services at least one thousand former Jihadis who had taken part in "holy wars" in the Middle East and Chechnya live in Belgium. These are people who have left Belgium to go to war and have then returned. The fighting had made them more radical.
Audenaert said that these are extremists, fundamentalists and experienced fighters, adding that he wasn't calling them terrorists but they could become terrorists.
"It's relatively young people who spent their youth in our country. Some also have Belgian citizenship. They left as 'jihadi' to Iraq, Pakistan, Afghanistan, Chechnya. They fought there against a diabolized enemy, under a foreign flag. Their war experience made them more extreme. Their discourse is more fundamentalist than ever."
Source: HLN (Dutch), Expatica (English)
See also: Belgium: Terror report