The Tunisian government says it has jailed or closely monitored 800 people who have returned from foreign battlefields in the past decade. Some of them fought for the terror group Islamic State.
Government spokesperson says some are in prison, under house arrest and others are under close surveillance.
Concern about their return has increased since Tunisian Anis Amri was identified as the suspected Berlin Christmas market attacker.
The national union of internal security forces has called on the government to strip Tunisian extremists of their nationality.
But President Beji Essebsi, citing the constitution, has said the authorities cannot prevent a Tunisian from returning home.