Police in Belgium have detained about 150 demonstrators as they tried to climb security fences outside Nato headquarters in Brussels.
Police used water cannon to stop protesters trying to climb fences
Organisers of the protest said they wanted to draw attention to what they called Nato's role in promoting war.
Water cannon was used to dislodge those who tried to get over the fences, some using mats to cover the barbed wires.
Police were prepared for the protest and had cordoned off a wide security perimeter around the Nato buildings.
Organisers Bombspotting and Vredesactie (Action for Peace) said about 500 protesters took part in Saturday's demonstration in the suburb of Evere to mark the fifth anniversary of the Iraq war.
They claimed Nato was the tool of US policy in Iraq and Afghanistan.