ATHENS - 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.In the central square next to parliament, four people dressed in German military uniforms and riding on a small jeep, waved black-white-and-red swastika flags and stuck their hands out in the Nazi salute.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 meters 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.She was given the red carpet treatment and full military honors 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.Political positioningAfter steering clear of Greece for the past five years, Merkel decided to visit now 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 neutralize 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 JP Morgan.Greece is in talks with its "troika" of lenders - the European Union, European Central Bank and International Monetary Fund - on the next tranche of a 130-billion-euro ($170-billion) loan package, its second bailout since 2010.Without the 31.5-billion-euro tranche, Greece says it will run out of money by the end of November.Many Greeks say they cannot take more of the wage cuts and tax hikes that have left a quarter of the workforce jobless and slashed the country's economic output by a fifth.Ties between Germany and Greece run deep. Thousands of Greeks came to Germany after World War Two as "guest workers" to help rebuild the shattered country and more than 300,000 Greeks currently reside there.But the relationship is clouded by the atrocities Greeks suffered at the hands of the Nazis during World War Two.Samaras' own great grandmother committed suicide when she saw Nazi tanks rolling down the streets of Athens after Germany occupied Greece, flying the swastika flag from the Acropolis.Greek President Karolos Papoulias, whom Merkel will also meet on Tuesday, fought against the German Wehrmacht as a teenager, before fleeing to Cologne to escape persecution by the Greek military dictatorship.The crisis has revived long-dormant animosities, with Greek protesters burning effigies of Merkel in Nazi gear and German media playing up images of lazy Greeks keen for German cash.Relations hit a post-war low early this year when Merkel's finance minister, Wolfgang Schaeuble, likened Athens to a "bottomless pit" and proposed imposing a European "Sparkommissar" on Greece to control its finances."The average German voter is irritated at the thought of dispatching more taxes or savings to feckless southerners, yet is desperate for the respect and goodwill to Germany that comes from public displays of magnanimity," said David Marsh, chairman of think tank OMFIF. "When Merkel flies to Athens, she's showing she's in charge, and she cares."In the center of Athens, the reception was less warm.Banners read "Merkel out, Greece is not your colony" and "This is not a European Union, it's slavery".Police have deployed 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.