Roel Stynen, a spokesman for the protesters, said Nato is "causing more problems than it solves".

The activists say the 26-nation alliance is not helping to bring peace around the world because some of its members still keep stockpiles of nuclear missiles and that it is fighting a losing war in Afghanistan.

They also demanded that Nato troops pull out of Afghanistan and that hundreds of American nuclear weapons at air bases in Europe, including in Belgium, be relocated back to the United States.