Greek workers began a two-day mass walkout on Tuesday, bringing public transport in Athens to a halt, as public anger mounts over a new government austerity bill aimed at securing international aid needed to prevent the debt-crippled nation from defaulting.

Public bus workers in the capital joined taxi drivers as well as metro, tram and train workers in the strike, paralysing traffic in the capital.

Many flights were to be cancelled or rescheduled as traffic controllers staged a three-hour work stoppage. Ferry services were also crippled, as ships linking to Greece's islands remained docked.

Judges and lawyers also joined the strike while publicly-run museums, archaeological sites and post offices were shut.

Police and anti-riot troops were out in force around parliament and government offices in Athens city centre, with water cannon at the ready to disperse the crowds in case of trouble arising from a demonstration called by the country's two main labour unions, the GSEE and ADEDY.

Thousands of people were streaming in to the capital join the rally.

"The people came here today to protest against the measures that bring us back centuries. They are abolishing our rights, and depriving our children's future," said teacher Thanassis Pargas.

Aleka Papariga, who leads the Communist Party, called for "systematic and well-organised disobedience not only to the government's decisions but to the overall system".

In parliament, lawmakers were debating the austerity bill, which proposes 18.5 billion euros ($23.6 billion) in new spending cuts and other reforms by 2016, adding to previous rounds of painful measures as the country heads for its sixth year in recession.

The package, which was put to parliament on Monday and will be voted on Wednesday, includes measures such as 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, judges, 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," said union activist Marie Lavrentiadou.

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

Implementing the austerity plan is a condition for Greece to qualify for a 31.5-billion-euro tranche of bailout funds from its troika of international creditors -- the European Union, International Monetary Fund and the European Central Bank.

Without it, Greece risks bankruptcy in mid-November.

"We must save the country from catastrophe," conservative Prime Minister Antonis Samaras said at the weekend, warning again that Greece could risk exiting the euro as he battles to win backing for the austerity measures from reluctant coalition partners.

Eurozone creditors were due to make a decision on the bailout funds -- part of a massive rescue package -- at a November 12 meeting of finance ministers.

"It is indeed important because there is... the need to fill in the financing needs of Greece in mid-November," EU Economic Affairs Commissioner Olli Rehn said on Monday after a Group of 20 meeting in Mexico City.

"Both the eurozone and the IMF and the Greek government and parliament are now on track in order to be able to take the decision next Monday."

Investors were banking on the austerity bill to pass, allowing Greece on Tuesday to raise 1.3 billion euros in a six-month bond issue at a slightly lower rate of 4.4 percent.

Finance Minister Yannis Stournaras last week unveiled the 2013 budget, which predicts that the economy will shrink by a worse than expected 4.5 percent next year and the country's debt mountain will swell to 346 billion euros or 189 percent of economic output.

While deeply resentful of the new cuts, some Greeks acknowledged that there may not be a better solution.

"We are in a state of compromise and we must bear the austerity measures as there is no turning back from the memorandum," said Mary Stirgepoulou, an 18-year-old university student.

"The main opposition criticises everything that is happening, it is just that I don't believe there is another solution. It would require a great effort for the measures to be overthrown."

Yannis Levas, 34, who works at a recruitment company aimed at finding jobs for Greeks abroad, called the measures "a double-edged sword".

"On the one side they must not go through, on the other they must. There is always that dilemma if we will return or not to the drachma," he said.