DHAKA: Belgium has placed Brussels at the highest terror alert level, citing a "serious and imminent threat that requires taking specific security measures as well as specific recommendations for the population."

The announcement by the Crisis Centre of the Belgian Interior Ministry is advising the public to avoid places where large groups gather -- such as concerts, sporting events, airports and train stations -- and comply with security checks, reports CNN.com

The rest of the nation will maintain its current terror level.

If people take the terror alert seriously, Brussels will be "shut down tomorrow," 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," he said. "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."

The increase in alert level for Brussels comes as authorities investigating last week's terror attacks in Paris conduct raids in Belgium as they work to identify and take down the network of terrorists behind the carnage.

Salah Abdeslam, 26, is the subject of an international search warrant. He was last seen driving toward the Belgian border when police stopped and questioned him a few hours after the attacks, not knowing that he was allegedly involved. His whereabouts are unknown.

ISIS has claimed responsibility for the Paris attacks.

BDST: 1200 HRS, NOV 21, 2015
RS