Greek police have used teargas and stun grenades to halt angry protesters in central Athens who tried to break through a barrier and reach the visiting German Chancellor Angela Merkel.
Tens of thousands of demonstrators defied a ban on protests to voice their displeasure with the German leader, who many blame for forcing painful cuts on Greece in exchange for two bailout packages worth more than €200 billion.
Some demonstrators pelted police with rocks, bottles and sticks, Reuters reports.
Mrs Merkel is visiting Greece for the first time since Europe's debt crisis erupted to deliver a message of support - but no new money.
During a joint news conference just a few hundred yards from the mayhem on Syntagma Square, outside parliament, Mrs Merkel reaffirmed Berlin's commitment to keep Greece inside Europe's single currency.
"I have come here today in full knowledge that the period Greece is living through right now is an extremely difficult one for the Greeks and many people are suffering," she said. "Precisely for that reason I want to say that much of the path is already behind us."
She tried to reassure her hosts that their reforms would eventually pay off, but also made clear that Greece, which has seen its unemployment rate surge to nearly 25% and economic output shrink by a fifth, would not solve its problems overnight.
Prime Minister Antonis Samaras promised to implement economic reforms necessary to restore confidence. "The Greek people are bleeding but are determined to stay in the euro," he said.
Some 6,000 police officers were deployed, including anti-terrorist units and rooftop snipers, to provide security during the six-hour visit. German sites in the Greek capital, including the embassy and Goethe Institute, were under special protection.