Thousands of Greeks massed outside parliament on Wednesday as lawmakers prepared for a late-night vote on a deeply unpopular new austerity package that is vital to unlock international aid and stave off imminent bankruptcy.

A general strike called by the two main labour unions paralysed Greece for a second straight day in a sign of anger at the 18.5-billion-euro ($23.6 billion) round of harsh cuts to pensions, salaries and welfare benefits.

Lawmakers had been locked in a fiery debate over the package, with main opposition party Syriza and the nationalist Independent Greeks failing in a motion challenging the legitimacy of the vote.

The package, which includes spending cuts and other reforms to be implemented by 2016, is necessary for Greece to unlock a 31.5-billion-euro ($40.2 billion) tranche of aid from its troika of international creditors -- the EU, International Monetary Fund and European Central Bank.

Without the austerity package, Greece risks running out of money on November 16, posing the biggest challenge to the coalition government led by conservative Prime Minister Antonis Samaris since it took office in June.

Finance Minister Yannis Stournaras had on Tuesday implored lawmakers to vote for the package, particularly reluctant members of the governing coalition, and observers expect parliament will approve the law.

"The country needs to implement a package of measures in order to eradicate the threat of bankruptcy for good," he said. "We are at the final, crucial crossroads and we have to make the right decision, otherwise our progress so far will be forever diminished."

Despite the looming bankruptcy and renewed warnings of a possible euro exit, many Greeks are angry at repeatedly having to tighten their belts.

More than 70,000 people joined the protest rally outside parliament called by the main unions, amid a heavy turnout of police who blocked off access to the area immediately surrounding the building.

"It is certain the austerity measures will pass, we have known this for a very long time. It is a very well organised and planned crime against Greece and its civilians," unemployed journalist Rena Maniou told AFP.

"I now comprehend the stories my grandparents described of the German occupation. Something similar is happening now, the only difference being things are a little worse this time around because they are selling out Greece," she added, reflecting anger among some at European paymaster Germany's tough fiscal demands.

The mass-selling Ta Nea newspaper branded the new austerity cuts as "poisonous", but said: "Even if they are painful, they are vital for the country to emerge from recession and kickstart the economy."

Rubbish piles up

Public transport in Athens was out of service for a second day, although the metro was running partial services to ferry protesters into the city centre.

Pharmacies were closed and rubbish collectors joined other civil servants including post office and museum workers on the strike, leaving the streets of Athens littered with trash bags.

Dimitris Tsikerdis, 35, an IT contract worker and Syriza voter, said he believed the legislation will pass.

But he said he would be joining Wednesday's protest even if demonstrations "have changed nothing in Greece, not even the results of our elections" in June which brought the Samaras government to power.

The measures under discussion include a rise in the retirement age to 67 from the current 65, and cuts of five to 10 percent in pensions of more than 1,000 euros a month.

Civil servants' 13th and 14th month pay would be scrapped, and further salary cuts imposed on academics, hospital doctors, diplomats and members of the armed forces.

"These measures essentially bring us many years back. All the labour rights the Greek people won post-World War II and post-dictatorship are taken back," union activist Marie Lavrentiadou said.

"The measures will be voted in, but the measures are not voted in the conscience of the Greek people and they can be ousted," she said.

The government however has warned that Greece has no choice but to adopt the measures if Greece wants to stay solvent and in the eurozone.

Eurozone creditors are due to make a decision on the release of the funds -- part of a massive rescue package for Greece -- at meeting of finance ministers on Monday.

One glimmer of hope emerged Wednesday, when the European Commission forecast that Greece would come out of recession in 2014 with growth of 0.6 percent after having shrunk by about a figth since the economic crisis broke.

However, in the 2013 budget unveiled last week, the finance minister predicted the economy would shrink by a worse than expected 4.5 percent next year while the debt mountain would swell to 346 billion euros or 189 percent of economic output.