A military police soldier patrols the Brussels Midi train station on Nov. 18, 2015. Belgium's national security level has been raised following reports that a suspect from last week's Paris attacks might be in the area. Dirk Waem/AFP/Getty Images

UPDATE: 10:15 p.m. EST: Belgian citizens are being advised to avoid places where large groups gather -- such as concerts, airports, sporting events and train stations -- and to comply with security checks, CNN reported. The advice comes from the Crisis Centre of the Belgian Interior Ministry. Brussels, the capital, will essentially be "shut down" Saturday if people take the terror alert seriously, CNN terrorism analyst Paul Cruickshank said.

"It suggests they have something specific and credible at the intelligence front pointing them in the direction that there may be a terrorist plot in the works," Cruickshank said, CNN reported. "It also suggests they don't have a handle on it, that they don't know where these plotters are or where they're coming from."

Original Story:

A fugitive gunman from the Paris attacks, who was said to be affiliated with the Islamic State group, was believed to be hiding in the Brussels area. Belgium’s government raised the metro area’s terror alert to the maximum level, Agence France-Presse reported Friday night. The Organ for the Coordination of Threat Analysis (OCAM), Belgium's national crisis center, warned of an “imminent threat.”

"Following our latest evaluation ... the center has raised its terror alert to level 4, signifying a very serious threat for the Brussels region," OCAM, which is part of the Belgian Interior Ministry, said in the statement. "The analysis shows a serious and imminent threat requiring specific security measures as well as detailed recommendations to the population.”

Salah Abdeslam, 26, reportedly fled the scene in Paris after the terrorist attacks last week and returned to his hometown near Brussels the morning after the shootings, ABC News reported. Police issued an international arrest warrant for Abdeslam, and described him as armed and dangerous. In the attacks that claimed 130 lives, Abdeslam was believed to have been one of the shooters who fired at civilians in a number of restaurants and cafes. Two of Abdeslam’s friends reportedly told ABC News that the fugitive had called them Tuesday evening, asking them to help him get back to Syria.