Belgian authorities say they have evidence to suggest more Islamic State recruits are looking to return to Europe.
The head of the government crisis center, Paul Van Tigchelt, told RTFB television, intelligence indicates foreign terrorist fighters in Syria want to return, "not just to Belgium, but to Europe to carry out an attack".
Belgium maintains its terror alert at the second highest level a month after suicide bombings killed 32 people in Brussels. Tigchelt said the terrorist threat to the country is "still considered serious, grave, and likely".
Investigations into the March 22 attacks claimed by IS militants continue amid tight security in airports, railway stations, and nuclear power stations.
Two suicide bombers at a Brussels airport and a third at Maalbeek metro station blew themselves up, marking the country's worst ever terror attack. A fourth bomber, Mohamed Abrini, could not detonate his device and was arrested on April 8 in Brussels.
A series of other arrests have been made in recent weeks as Belgian authorities try to uncover a terrorist network linked to both the attacks in Brussels as well as the November 13th attacks in Paris.