* Nearly 70,000 take to streets to protest
* First big strike for new government
* Transport services disrupted, offices shut
* Hooded youths hurl petrol bombs at police
By Renee Maltezou and Harry Papachristou
ATHENS, Sept 26 (Reuters) - Greek police clashed with hooded rioters hurling petrol bombs as tens of thousands took to the streets of Athens on Wednesday in Greece's biggest anti-austerity protest in more than a year.
Violence erupted after nearly 70,000 people marched to parliament chanting "We won't submit to the troika (of lenders)" and "EU, IMF Out!" on the day of a general strike against a new round of cuts demanded by foreign lenders.
As the rally ended, dozens of black-clad youths 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 small blazes in the streets.
About 120 people were detained after angry protesters smashed bus stop kiosks and set fire to garbage cans.
"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 24-hour nationwide strike, 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 near-bankrupt Greece first resorted to aid from international lenders in 2010 - which has come at the price of painful austerity cuts.
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 say the lull is over.
"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 p u blic 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. Train service and flights were suspended, public offices and shops were shut, and hospitals worked on skeletal staff as part of the general strike.
Much of the union anger is directed at spending cuts worth nearly 12 billion euros ($15.55 billion) 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 favour 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 and nearly one out of four jobless, analysts say patience is wearing thin and a strong public backlash could tear apart the weak 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."