Tens of thousands of Greeks poured into the streets on Tuesday as mass strikes paralysed Athens in the latest show of anger over a new austerity bil aimed at securing international aid needed to prevent the debt-crippled nation from defaulting. Lawmakers were debating the controversial austerity package, 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. Police and anti-riot troops were out in force around parliament and government offices in Athens, in case trouble arose from a demonstration called by the country\'s two main unions to coincide with the start of a 48-hour general strike. The demonstration, however, ended without incident. A public transport work stoppage that began on Monday widened on Tuesday, with bus workers joining taxi drivers as well as metro, tram and train workers in the strike, paralysing traffic in the capital. Many flights were cancelled or rescheduled as air traffic controllers staged a three-hour work stoppage. Ferry services were also crippled, with 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 estimated that 40,000 people turned out at the Athens rally on Syntagma Square near parliament, with banners screaming \"No to measures of impoverishment\" and \"The people above everything else -- not numbers and measures.\" In the northern city of Thessaloniki, 20,000 joined a march. \"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 in Athens. Alexis Tsipras, leader of the main radical left opposition party Syriza who took part in the protest, said Greece\'s coalition government was \"ridiculing\" the constitution. 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\". The austerity bill was submitted to parliament on Monday and will be voted on Wednesday. Measures 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, 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 receive 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 running out of money on November 16 when a debt repayment falls due. Securing the next aid tranche is \"necessary to avoid default and bankruptcy,\" Finance Minister Yannis Stournaras said Tuesday. Prime Minister Antonis Samaris, battling to win support for the austerity bill from reluctant coalition partners, had warned at the weekend that Greece could exit the euro, declaring: \"We must save the country from catastrophe.\" Jean-Claude Juncker, head of the Eurogroup finance ministers, voiced optimism about the prospects of  Greece implementing the necessary reforms. \"Our Greek friends don\'t have different options or another choice. They have to do it,\" he said in Singapore. Eurozone creditors were due to make a decision on the bailout funds -- part of a massive rescue package for Greece -- at a November 12 meeting of finance ministers. \"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,\" EU Economic Affairs Commissioner Olli Rehn said on Monday after a Group of 20 meeting in Mexico City. Investors were banking on the austerity bill passing, 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. 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 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.