Greek police fired teargas and stun grenades at protesters in central Athens on Tuesday when they tried to break through a barrier and reach visiting German Chancellor Angela Merkel.
Tens of thousands of demonstrators defied a ban on protests, gathering in Syntagma square to voice their displeasure with the German leader, who many blame for forcing painful cuts on Greece in exchange for two EU-IMF bailout packages worth over 200 billion euros.
Some pelted police with rocks, bottles and sticks, and tried to bust through a barricade set up to protect Merkel and her delegation, who were meeting with Prime Minister Antonis Samaras at his office several hundred metres away.
Police detained dozens of protesters in what they said was one of the biggest demonstrations in months.
Merkel is visiting Greece for the first time since Europe's debt crisis erupted here three years ago to deliver a message of support - but no new money - to a nation hammered by recession and fighting to stay in the euro.
Police have readied 6,000 officers, 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, are under special protection.
Merkel was given the red carpet treatment and full military honours when she arrived at Athens airport in the early afternoon. Samaras greeted her with a handshake as she exited the German air force jet and a band played the German and Greek national anthems.
In the centre of Athens, the reception was less warm. On Syntagma square, four people dressed in German military uniforms rode around on a small jeep, waved black-white-and-red swastika flags and stuck their hands out in the Nazi salute.
Banners read "Merkel out, Greece is not your colony" and "This is not a European Union, it's slavery".
After steering clear of Greece for the past five years, Merkel decided to visit for several reasons.
She wants to show support for Samaras, a fellow conservative, as he struggles to impose more cuts on a society fraying at the edges after five years of recession.
At a joint appearance before the press, she is expected to confirm her desire to keep Greece in the euro zone, after members of her government flirted with the idea of an exit earlier this year.
With a year to go until Germany holds an election, Merkel also hopes to neutralise opposition criticism that she has neglected Greece and contributed to its woes by insisting on crushing budget cuts.
"Her visit to Athens is primarily about political positioning, and the opportunity to clarify her position on Greece," said Alex White, an analyst at J.P. Morgan.
(Additional reporting by Tatiana Fragou, Lila Chotzoglou, Renee Maltezou, Daphne Papadopoulou and Dina Kyriakidou in Athens and Tom Kaeckenhoff in Bonn; Writing by Noah Barkin and Matt Robinson; Editing by Dina Kyriakidou)