A major police operation is ongoing in Brussels after four officers were shot during an anti-terror raid linked to the Paris attacks.

The gun battle began around 3pm local time. Two suspects, reportedly wielding Klashnikovs, opened fire, leaving four officers injured, one seriously.

They fled the scene via rooftops, according to witnesses, and were believed to be holed up in a building.

At least one of the men has been gunned down, according to reports.