In Athens, police clashed with protestors at an anti-austerity demonstration outside the Greek parliament building.

During the otherwise peaceful rally, police fired tear gas on a group of youths who were throwing rocks and firebombs at both the police and the government headquarters itself.

The 20,000-strong rally is a demonstration against proposed budget cuts meant to assuage the nation's crippling debt crisis. The austerity plan is part of a deal between Greece, the European Union and the International Monetary Fund, and can be seen as collateral for a large loan.

The austerity measures would include cuts to public services and an increase in taxes. Protestors in Athens' Syntagma Square chanted enough with the lies, enough with the bankers, enough with the EU and IMF. Revolt, revolt!

Twelve people were arrested for throwing eggs and water bottles at members of Parliament.

The massive demonstration was part of a 24-hour strike organized by the nation's two largest labor unions, the Civil Servants' Confederation (ADEDY) and The General Confederation of Greek Workers (GSEE).

The unions demand the immediate withdrawal of the new, harsh and unjust measures that the government is proposing, the unions said in a joint statement. GSEE and ADEDY are continuing their struggle to reject these anti-worker and antisocial measures.

While the protest was mostly peaceful, self-described anarchists came wielding rocks and covered their faces with hoods and t-shirts. Police were prepared for the violence, erecting steel barricades and parking buses in strategic locations. There were a reported 5,000 police on duty.

Greece has been strife with unrest over the past year. The country has teetered on the edge of default since the spring of last year, when a number of loan deadlines expired in just a few weeks.