Anti-globalisation protesters have pushed back police lines guarding a lakeside conference centre due to host a meeting of European Union foreign ministers later today.
About 400 activists shunted police in riot gear down the narrow streets of Riva del Garda, a picture-postcard town at the head of Lake Garda in northern Italy.
The demonstrators, some wearing motorcycle helmets, took over the town square and attacked four parked police cars, breaking the windows and smearing slogans on the doors.
Blue-helmeted police regrouped at the entrance to an inner security cordon set up around the venue of the two-day informal meeting of EU ministers.
Some of the demonstrators fired off pink flares towards the police, the bangs echoing around the mountain-ringed town, but the police stood their ground and did not respond.
After an hour-long stand-off, the crowd broke up and headed to a congress centre on the outskirts of town where various pressure groups are holding four days of debates.
The "disobedients" say up to 20,000 demonstrators will descend on Riva del Garda tomorrow to protest against EU trade and foreign policies.
Anti-globalisation groups normally shun informal EU gatherings, but the Italian meeting comes days before the start of world trade talks in Cancun, Mexico, and activists want to seize the initiative in the run-up to that event.
EU foreign ministers were due to arrive in town by boat and helicopter later today, with their talks expected to include Iraq, Middle East peace and a new European constitution.