Athens protesters clash with police Reuters

Hooded youths on the fringes of a major anti-austerity protest in Athens have thrown rocks and firebombs in violent clashes with police at the Greek parliament.

At a rally of more than 20,000 in Syntagma Square, police responded with teargas to push the protesters away from barricades erected to protect the parliament building where the government is seeking support for new cutbacks required to avoid a debt default.

Other demonstrators who had been part of the previously peaceful gathering also clashed with the violent groups of hooded youths, trying to eject them from their rally.

The protests were part of a 24-hour general strike against the cutbacks, which the country must pass to continue receiving funding from a €110bn (£95bn) international bailout that is preventing Greece from defaulting on its debts.

A large part of central Athens was closed to traffic and pedestrians as police mounted a huge security operation to allow politicians access to parliament by car. Around 5,000 officers, including hundreds of riot and motorcycle police, used parked buses and crowd barriers to prevent protesters from encircling the building.

"Resign, resign," the crowd chanted. The protesters included both young and old, and many brought their children, hoisting them on to their shoulders to shield them from the crush.

Two separate marches organised by trade unions joined the rally in Syntagma. Such demonstrations have often turned violent in the past – three clerks died when rioters torched a bank in Athens last May.

But the latest austerity drive has brought many people on to the streets for the first time.

"What can we do? We have to fight, for our children and for us," said Dimitra Nteli, a nurse at a state hospital who was at the protest with her daughter. "After 25 years of work I earn €1,100 a month. Now that will drop to €900. How can we live on that?"

Her 26-year-old daughter, Christina, said the situation in Greece had led her to leave for the UK to study conflict resolution. "I have no job here. There are no prospects," she said.

A police spokesman, Athanassios Kokalakis, said 10 protesters were briefly detained. About a hundred people booed and heckled as cars carrying the prime minister, George Papandreou, and President Karolos Papoulias swept past for a meeting.

The general strike crippled public services across the country, leaving state hospitals running on emergency staff, disrupting port traffic and public transport, and forced radio and television news programmes off the air during the morning. Journalists' unions called off their strike to cover developments in Athens.

Flights, however, were operating normally after the air traffic controllers' union called off their participation in the strike.

"They keep asking us to give more," said Ilias Iliopoulos, the general secretary of the civil servants' union ADEDY. "Now, again, they will cut our salaries and bonuses, from the little we have left."

The government needs to pass a 2012-2015 austerity programme worth €28bn this month or face being cut off from continued funding from the EU and IMF.

To meet their commitments, Papandreou's Socialists have abandoned a pledge not to impose new taxes and have drawn up a four-year privatisation programme worth €50bn, further fuelling protests against austerity by public utility employees and other affected groups.

Some of the MPs from the governing party have publicly criticised the cuts. One of them defected on Tuesday, reducing Papandreou's parliamentary majority to five in the 300-seat legislature. Another Socialist MP said he would vote against the bill.

With its credit rating slashed, Greece is being kept afloat by the bailout, but will need extra support to cover funding gaps next year as high interest rates will prevent it from tapping the bond market, contrary to what the original bailout agreement had predicted.

On Monday night, Standard & Poor's cut Greece's rating from B to CCC, dropping it to the very bottom of the 131 states that have a sovereign debt-rating. That suggests Greece's creditors are less likely to get their money back than those of Pakistan, Ecuador or Jamaica.

It is an astonishing low for Greece. As recently as January 2009, the country still had a stellar A rating despite a hefty debt burden.

The Socialists' popularity has plummeted in recent weeks. A weekend opinion poll gave the main opposition conservatives a four-point lead, the first time the party has been ahead since 2009. The next general election is scheduled for October 2013.