Greek police fired teargas at hooded youths hurling petrol bombs and stones as tens of thousands took to the streets in Greece's biggest anti-austerity demonstration in months on Wednesday.

The clashes occurred after more than 50,000 people marched to parliament chanting «We won't submit to the troika (of lenders)» and «EU, IMF Out!» on a day of strikes against a new round of cuts demanded by EU and IMF lenders.

As the rally ended, dozens of black-clad youth threw stones, petrol bombs and bottles at riot police, who responded with several rounds of teargas. Police chased the protesters through Syntagma square in front of parliament as helicopters clattered overhead. Smoke rose from a small blaze in a corner.

The strikes, called by the country's two biggest unions representing half the four-million-strong work force, is shaping up to be the first test of whether Prime Minister Antonis Samaras can stand his ground.

Police officials estimated the demonstration was the largest since a May 2011 protest, and among the biggest since Greece first resorted to aid from international lenders in 2010.

"We can't take it anymore - we are bleeding. We can't raise our children like this,» said Dina Kokou, a 54-year-old teacher and mother of four who lives on 1,000 euros a month.

"These tax hikes and wage cuts are killing us."

The traditional summer break has allowed the fragile conservative-led coalition to enjoy relative calm on the streets since narrowly coming to power on a pro-euro, pro-bailout platform, but unions predict an end to the lull.

"Yesterday the Spaniards took to the streets, today it's us, tomorrow the Italians and the day after - all the people of Europe,» Yiorgos Harisis, a unionist from the ADEDY public sector group told demonstrators.

"With this strike we are sending a strong message to the government and the troika that the measures will not pass even if voted in parliament, because the government's days are numbered."

About 3,000 police - twice the number usually deployed - stood guard in the centre of Athens, which last saw serious violence in February when protesters set shops and banks ablaze as parliament approved an austerity bill.

Police formed a barricade outside parliament, and officers blocked a pensioner who tried to move towards Samaras's office holding a banner with pictures of Greek prime ministers under the title: «The biggest traitors in Greek history».

Ships stayed docked, museums and monuments were shut to visitors and air traffic controllers walked off the job for a three-hour stoppage.

Much of the union anger is directed at spending cuts worth nearly 12 billion euros over the next two years that Greece has promised the European Union and International Monetary Fund in an effort to secure its next tranche of aid.

The bulk of those cuts is expected from cutting wages, pensions and welfare benefits, heaping a new wave of misery on Greeks who say repeated rounds of austerity have pushed them to the brink and failed to transform the country for the better.

"We can't just sit by idly and do nothing while the troika and the government destroy our lives,» said Dimitra Kontouli, a 49-year-old local government employee whose salary was cut to 1,100 euros a month from 1,600 euros previously.

"My husband has lost his job, we just can't make ends meet."

A survey by the MRB polling agency last week showed that more than 90 percent of Greeks believe the planned cuts are unfair and burden the poor, with the vast majority expecting more austerity in coming years.

Unions argue that Greece should remain in the euro but default on part of its debt and ditch the current recipe of austerity cuts in favor of higher taxes on the rich and efforts to nab wealthy tax evaders.

But with Greece facing certain bankruptcy and a potential euro zone exit without further aid, Samaras's government has little choice but to push through the measures, which have also exposed fissures in his coalition.

With Greece in its fifth year of recession, analysts say patience is wearing thin and a strong public backlash could tear apart the conservative-led government.

"What people want to tell Samaras is that they are hurt and Samaras could use this to demand concessions from the troika,» MRB polling director Dimitris Mavros said.

"The people are willing to give the government time, but on certain conditions like cracking down on tax evasion and securing a bailout extension. If the government succeeds in that, its life will also be extended."

[Reuters]