Via BBC: 

Police in Brussels have surrounded a man who was behaving suspiciously and wearing "a long coat with protruding wires", Belgian media report.

A large police operation is underway near Place de la Monnaie in the centre of the Belgian capital.

The bomb squad is present. Shops nearby have been evacuated and several streets are closed.

Photos from the scene show a man kneeling with his hands up, while police point their guns at him.

Police say that they have the suspect "under control" but have not yet arrested him.

The incident comes a day ahead of Belgium's National Day, with heightened security in Brussels for the festivities.

Update:

Well now I've heard everything. The man in the winter coat with wires sticking out?

Via BBC:

The city was on high alert ahead of Belgium's National Day on Thursday. An attack in Nice on France's Bastille Day last week left 84 people dead.

The bomb squad was called, shops evacuated and several streets closed.

"We got a call about someone acting suspiciously. Someone with a heavy winter coat – in these temperatures it's very suspicious.

"And there were wires coming out of the coat too," Christian De Coninck of Brussels police told Belgian TV. "We didn't take any risks. The person was stopped and kept at a distance."

It was 30C in Brussels on Wednesday afternoon.

Thirty-two people were killed in bomb attacks in Brussels earlier this year.