Police fired tear gas on Tuesday to disperse protesters attempting to storm a barricade near parliament as tens of thousands of Greeks massed in Athens in a show of anger against German Chancellor Angela Merkel.
Vilified for Greece's punishing spending cuts, Merkel, the leader of Europe's paymaster, is on her first visit to the eurozone's most indebted nation since the debt crisis erupted almost three years ago.
As she met Greek Prime Minister Antonio Samaras, demonstrators gathered just a few blocks away, some brandishing banners reading "You are not welcome, Imperialisten Raus" (Imperialists out)" or "No to the Fourth Reich".
Two Nazi flags were draped on the steel fence near parliament and set on fire. Sporadic violence also broke out, with small gangs of masked youths throwing bottles at riot police.
Thousands of police were out on the streets and key parts of central Athens were closed off to create a large security zone for Merkel's meetings with Samaras and President Carolos Papoulias.
Police said about 25,000 protesters had already streamed on to the central Syntagma Square, which lies outside the lockdown zone.
Merkel, the head of Europe's largest economy and the continent's paymaster, has been a champion of tough budgetary discipline.
She has become a hate figure in Greece over the tough spending cuts imposed on the country in return for multi-billion dollar aid packages.
She has even been depicted as Adolf Hitler in Greek tabloid caricatures.
The visit comes at a crucial time for Athens which is locked in negotiations with its international creditors over a 13.5-billion-euro package of further cuts in order to win further bailout funds.
Christina Vassilopoulou, a 37-year-old teacher in the impoverished Athens district of Agios Panteleimon, said she had turned up to protest "the decisions taken at European meetings where Merkel manipulates the participants".
"I have a doctorate and I make 900 euros a month, 400 less than before. We have children that go hungry and most of the parents are unemployed," she said.
Merkel's office and the Greek authorities are selling her visit as a gesture of solidarity and encouragement for the country's reform efforts, but many in Greece said the trip only served to fan anger.
Online hackers group Anonymous said it had attacked a number of Greek government sites.
"We, as Anonymous, are next to the Greeks claiming their freedom. We are next to a people who have fought against the German occupying forces," it said.
Vana Koronaiou, a shop owner selling German-made handbags near Syntagma Square, said: "This visit pours oil on the fire.
"If she wanted to help, she should have done it sooner," she told AFP.
Samaras is holding talks with Merkel before a joint press conference. The German chancellor will then meet Papoulias and a delegation of Greek and German businessmen before departing in the evening.
Shortly before her arrival, Greece's international creditors -- the International Monetary Fund, the European Union and the European Central Bank -- piled further pressure on Athens to live up to its austerity pledges made in exchange for crucial loans.
However, Athens and Berlin both shied away from tough talk ahead of the visit.
"The basic message is that we are here, that we are on the side of Greece, and that we want to support Greece's endeavour towards stability and recovery," German ambassador to Greece Wolfgang Dolt told state television NET.
"The people in this country are going through tough measures, massive adjustment, structural reforms, they are under great pressure," Dolt said.
"They deserve respect for that. I think this is one of the core sentiments we have and which will certainly be expressed."
Greek government spokesman Simos Kedikoglou described the visit as "a message of faith in the course of the Greek government, the Greek economy".
"It is a positive step, it's important that the German chancellor is coming to Greece for the first time since the start of the crisis," he said.
Mocking the government's positive spin on the visit, a front-page cartoon in top-selling Ta Nea daily showed Samaras sweeping protesters under a red carpet as Merkel's plane lands.
Greece is counting on a positive outcome from the EU-IMF talks to unblock a 31.5-billion-euro installment from Greece's EU-IMF bailout package, which is needed to recapitalise banks and repay outstanding domestic debts in a country that is heading for a sixth straight year of recession.
Samaras said Friday that his country could not take more bitter medicine and warned that if the next aid tranche did not arrive soon, state coffers would be empty by November. Greece's debt amounted to about 160 percent of gross domestic product in 2011, according to official figures.
International creditors on Monday gave Athens an October 18 deadline -- the date of the next European Union summit -- to implement reforms in exchange for slice of loan, which has been pending since June.
"We stressed that before the next disbursement, Greece clearly and credibly should demonstrate its commitment to fully implement the programme -- and 89 prior actions from March should be implemented by the 18th of October at the latest," Eurogroup chairman Jean-Claude Juncker said at the close of talks with finance ministers from the 17-nation single currency area.