London: A high alert has been sounded in Europe following anti-terror raids and arrests of suspected militants.
Security has been tightened in several European countries after last week`s attacks in Paris which left 17 people dead.
More than 20 people have been arrested in Belgium, France and Germany. Belgium has joined France in deploying troops alongside police, BBC reported.
There are increased concerns about the return of young Europeans who have gone to fight with Middle East militants.
In Belgium, five people were charged Friday with "participating in the activities of a terrorist group" following a series of raids that began Thursday evening and left two suspects dead.