Clashes between hooded youths and anti-riot police erupted in central Athens on Wednesday during a mass protest against severe government austerity measures.

One elderly civilian was slightly injured and taken to a hospital during the clashes, said eyewitnesses and local journalists, who joined a 24-hour nationwide general strike thath has paralyzed public services, hospitals and mass transportation across the cash-strapped country.

The strike also has led to the cancellation of more than 100 flights at Athens International Airport and closed the Acropolis and other major tourist sites.

The rally was part of Greece's first major labor protest this year as Prime Minister George Papandreou's Socialist government faces international pressure to make more lasting cuts after the nation's debt-crippled economy was rescued from bankruptcy by the European Union and the International Monetary Fund.

Thousands of demonstrators remained at Syntagma square in front of the Greek parliament as groups of hooded youths threw rocks and Molotov bombs at policemen who respond with tear gas and flash grenades, blanketing parts of the city center in choking smoke.

Protesters chanting "Don't obey the rich -- Fight back!" marched to parliament as the city center was heavily policed. A brass band, tractors and cyclists joined the rally.

Unions are angry at the ongoing austerity measures put in place by the Socialist government in exchange for a 110 billion euro (150 billion U.S. dollar) bailout loan package from European countries and the IMF.

Police were on high alert because violence has marred many previous rallies in Greece during the past year.

On May 5, 2010, three bank employees died during an attack by hooded arsonists at a bank branch near the parliament.

Elsewhere, about 15,000 people rallied and minor scuffles broke out in Greece's second largest city, Thessaloniki, while Stathis Anestis, deputy leader of Greece's largest union, the GSEE, said around 60 demonstrations were being planned in cities and towns across Greece. He said the GSEE was in talks with European labor unions to try and coordinate future strikes with other EU countries.