During the Cold War, Prague was a clearing house for international terrorists trained and equipped by the KGB and its east-bloc clones. The Czech intelligence service was heavily co-opted by the KGB, and used to coordinate the KGB's wet work with the Bulgarians.
Old habits die hard, and terrorists trained during the cold war tend congregate in Prague--like homing pigeons returning to roost--to hook up with their old (and largley mafia employed) ex-bosses.
The new Czech government is trying hard to root all of this out and clean up its act. But draining the swamp is easier said than done.