With helicopters circling overhead, hundreds of activists tried to break through walls of police clad in black, full-body armor as they marched on the meeting hall, where convention organizers opened the European Economic Summit.
At one point, they pelted police with bottles and sticks causing officers to charge the crowd, batons swinging.
Authorities had earlier sealed off the convention hall with rings of barricades that turned this ancient alpine tourist destination into a fortified maze of checkpoints.
Waving communist hammer-and-sickle flags, the activists were repeatedly turned back. They continued chanting, "Our world is not for sale, put the bankers into jail!"
Despite the scuffles, it was business as usual inside the gleaming convention hall built especially for the summit. The event, hosted by the World Economic Forum and chaired by billionaire financier George Soros, runs through Tuesday.
Topping the agenda Sunday was the issue of European Union enlargement.
Nearly all panelists, mostly from central and eastern Europe, applauded the breakthrough agreement last month in Goteborg, Sweden, when the European Union agreed to admit new members from the formerly communist east by 2004.
"Nobody questioned the idea of enlargement," said Guenter Verheugen, the European commissioner overseeing the complex entry negotiations. "For the 15 member states, it's strategic objective Number One. For candidate countries, it's a light at the end of the tunnel."
Representatives from candidate countries remained upbeat that their membership bids would not be delayed by a June 7 Irish vote rejecting the treaty that prepares the way for expansion.
But they also warned that leaders in EU and candidates countries need to try harder to sell enlargement to their citizens.
"We shouldn't exaggerate this referendum," Polish President Aleksander Kwasniewski said. "We have to show them that their interests are protected and that enlargement is good for all of Europe. He added that Poland was still pushing to wrap up negotiations in 2002 and be among the first group of entrants.
Hungary, Poland, Slovenia, the Czech Republic, Cyprus and Estonia are expected to be the first to join the European Union. Slovakia, Malta, Latvia and Lithuania - which started talks later - are also making good progress.
Verheugen said Sunday that all candidates except Romania and Bulgaria have a shot at joining the European Union as early as 2004.
Even countries not in the running championed European expansion Sunday.
"The enlargement process is of special interest and importance in the Balkan countries," said Zoran Djindjic, prime minister of Serbia, the larger of the two remaining Yugoslav republics.
"We are thregion that is under the highest danger of disintegration," Djindjic said, adding that EU enlargement would allow the Balkans region to "focus on integration instead of disintegration."
Anti-globalization protesters and self-stylized anarchists were less convinced of the summit's agenda. Sunday's clashes injured at least two protesters and one police officer.
The unrest came after street fighting left 70 people injured at the Goteborg summit and similar rioting injured 32 people at an anti-World Bank rally last weekend in Barcelona, Spain.
Local press reports estimated nearly 5,000 police were on duty to try and prevent similar mayhem from erupting in the hometown of Wolfgang Amadeus Mozart.
After boxing in about 300 protesters late Sunday evening, police chief Karl Schweiger offered to let free any activist willing to be searched and provide identification.
Minutes later, a hail of bottles and sticks rained down on his officers, who then charged the crowd. Police spokeswoman Sonja Fiegel said 11 activists were arrested for disorderly conduct.
By Hans Greimel
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