Water cannons were seen among police reinforcements around the alliance complex on the outskirts of the Belgian capitals, where anti-war protestors were planning to demonstrate later in the day.

Nearly 100 police were also deployed in the grounds of the headquarters, while journalists were subject to tightened checks as they entered the compound.

Belgium is fiercely anti-war. Tens of thousands have attended demonstrations in February and March, while smaller protests are held regularly on Thursday evenings outside the US embassy.

Most of the protests have been peaceful, but police have had to use tear gas and water cannons to break up demonstrations, notably during an EU summit on March 20-21.

SPACE.WIRE