UPDATE 8am: The Greek parliament has approved a slashed 2013 budget which will secure the release of foreign aid vital to save the debt-ridden country from insolvency.
The vote marked another step in the government coalition's efforts to meet the demands of its creditors after a separate package was approved on Wednesday.
The austerity measures, which will result in salary and pension cuts across the board, are deeply unpopular and have fuelled sometimes violent protests in the capital Athens.
According to an AFP count, more than 150 of parliament's 300 members voted in favour of the budget, paving the way for the European Union, International Monetary Fund and the European Central Bank to unlock 31.5 billion euros ($A38.82 billion).
During the debate preceding the vote, Finance Minister Yannis Stournaras said the budget, which includes 9.4 billion euros in cuts, would guarantee the funds.
"I assure you in the most categoric manner that the tranche (of aid funds) will be released in an imminent fashion,” he said.
Europe's paymaster Germany was less categorical earlier this week and said the ball was in the Greek camp.
Police estimated that around 15,000 protesters had massed outside parliament before the vote.
"The measures will pass but we are here to prove that we are not resigned to it,” Olga P., 35, an English teacher in a public school, said before the vote.
Sunday's protest was called by both the public-sector Adedy union and the private-sector GSEE union.
A GSEE statement called urged to reject the austerity policies.
A banner from the opposition radical left-wing Syriza party called for the government's downfall.
The country is currently surviving on two massive bailouts from its international creditors.
The vote came on the eve of a eurozone finance ministers meeting, during which Athens' progress on carrying out required reforms and cuts will be scrutinised.
Without the fresh funds, Greece risks default on November 16, when the government -- in the midst of its biggest crisis since taking office in June -- must repay a three-month treasury bill worth five billion euros.
German Finance Minister Wolfgang Schaeuble said in an interview with Sunday's Die Welt newspaper that the ball was in Greece's court even after MPs approved the latest 18.5 billion euro austerity package demanded by creditors.
"Nobody in the eurozone opposes the idea of accepting the payment of the next tranche of aid,” he added.
"But only when the conditions have been met. And that, that is for the government in Athens to take care of."
The 2013 budget predicts the economy will shrink by a worse-than-expected 4.5 per cent next year, the sixth year of recession, while the public deficit -- the shortfall between government revenue and spending -- is forecast to rise to 5.2 per cent of gross domestic product.
Deputy finance minister Christos Staikouras however said the government could for the first time in years register a primary budget surplus -- before debt servicing costs -- next year.
Public debt is expected to swell to 346 billion euros, a massive 189 per cent of economic output, compared with a target set by creditors who want the figure slashed to 120 per cent of GDP by 2020.
The 9.4 billion euros in cuts will mainly hit state wages, pensions and benefits, already drastically reduced over the past two years in a country where unemployment is now at a record level of more than 25 per cent.
But the government will still need to borrow over 68 billion euros next year, according to the budget.