Belgian police used water cannon and tear gas yesterday to disperse masked protesters wielding cobblestones and metal staves during an anti-globalisation demonstration outside the summit.
It was the first serious outbreak of violent protests since the September 11th attacks on the US and recalled similar clashes at an EU summit in Sweden last June and at a meeting of the world's richest countries (G7) in Italy in July.
Witnesses said the rioters, some dressed in black and wearing heavy boots, smashed the windows of banks in Place Bockstael, a square about three kilometres from the Laeken royal palace where the summit was being held.
They also hurled a metal barrier through the windows of a police station, wrecked several parked cars and daubed anti-capitalist slogans on boarded-up shop windows.
Police in riot gear surrounded a hard core of several hundred demonstrators and systematically searched people wanting to leave the area, confiscating sticks and stones.
They turned on about four water cannon in the Avenue du Port after protesters built fires on the street, and used loudhailers to urge the rioters to disperse.
Police said they had charged several protesters and had arrested one woman.
The riots erupted after about 8,000 demonstrators, far fewer than originally expected, had marched peacefully through an unusually chilly Brussels calling for an end to war and to economic inequalities.
The mood of the marchers was festive and relaxed as they danced, sang, blew whistles and beat drums.
Only a few protesters were hooded and masked.
A mixed bag of anti-globalisation activists, anarchists and environmentalists, they brandished banners saying "Not in my name: stop the war!" and "Stop the massacre, free Palestine!"
Many of the protesters chanted anti-war slogans.
"Good for the rich, bad for the poor. We don't want your capitalist war," one group chanted in English.
Anti-globalisation protesters have increasingly pushed the anti-war theme since the US attacks in Afghanistan.