By Michele Kambas and Philip Pangalos
THESSALONIKI, Greece (Reuters) - Police have arrested scores of protesters, including 12 foreigners, after breaking up riots in Greece's second largest city in which shops were smashed and buildings set ablaze, including a McDonald's.
A group of 200 self-styled anarchists were among 25,000 mainly peaceful anti-capitalist protesters who marched in late afternoon on Saturday through Thessaloniki's centre, about 80 km (50 miles) west of where a European Union summit ended earlier in the day.
"They threw petrol bombs into the McDonald's and planted anarchist black flags on the footpath outside," Reuters correspondent Philip Pangalos said. "Others attacked nearby shops with axes and sticks."
Demonstrators also torched a Vodafone store, witnesses said.
About 30 shops as well as three branches of Greek banks were badly damaged with windows smashed and petrol bombs thrown inside.
Riot police used baton charges and teargas to drive the attackers away from an area about half a kilometre from the U.S. consulate.
About a dozen shop and building entrances as well as five cars were still ablaze two hours after the violence erupted. Thick smoke and clouds of teargas billowed from the city centre.
"This is like an urban war zone, everything is on fire," said resident Maria Hounda said.
A senior police official said 84 people had been arrested, including three Austrians, three Americans, two Britons, a Cypriot, one Canadian, one German and a Frenchman.
"Those arrested, including the foreigners, will appear before the public prosecutor tomorrow morning," the official told Reuters.
In an effort to avoid the kind of street clashes that marred the 2001 Group of Eight summit in Genoa, Greece switched the EU meeting from the port of Thessaloniki to the seaside resort of Porto Carras, which was more easily sealed off.
With protest groups promising demonstrations against the EU, NATO and the U.S.-led war in Iraq, Greece had deployed 16,000 troops and police across the scenic coastal region and Thessaloniki in the country's biggest ever security operation.
Reuters correspondent Michele Kambas said the anarchists, most of them wearing ski and gas masks, were "very well equipped".
"They used crow bars to tear off aluminium sheeting that many shopkeepers and banks had erected days ago to cover their premises in expectation of trouble," Kambas said.
The demonstrators were overwhelmingly Greek, although there was a sprinkling from Britain, Germany, Scandinavia and Italy.
The police charges drove the attackers into sanctuary in the city's university, the country's largest. By law police are not allowed into university grounds.