Excerpt:
Already wrestling with a constantly-evolving terror threat, European intelligence agencies spy a new problem on the horizon: hundreds of jihadists due to be released from prison.
Battling to stop further attacks like those seen everywhere from London to Paris, Brussels to Barcelona, freshly-released prisoners will add to agencies’ surveillance burden.
Although many may go on to lead peaceful lives after prison, some may not -- and officials admit they have so far given insufficient attention to working out the scale of the threat.
They are already working to keep track of jihadists returning from the battlefield in Iraq and Syria, and homegrown radicals who investigators fear could launch an attack at any moment.