Workers in Greece are staging a 48-hour general strike across the public and private sectors in protest at a proposed new wave of austerity.
Public transport has been shut down, but fewer people have demonstrated than during previous stoppages.
MPs are due to vote on the package of salary and pension cuts, and labour market reforms, on Wednesday.
Greece must back the measures, and the 2013 budget, to receive the next part of a bailout and avoid bankruptcy.
The latest strike, called by Greece's two biggest labour unions, representing half the four million-strong workforce, started at midnight.
Trains, ferries and some international flights have all been cancelled, schools closed, and hospitals reportedly open only for emergencies.
It's the third major walkout in two months as Greece tries to reduce its budget deficit in line with international demands.
The BBC's Mark Lowen in Athens says that with proposals for a fifth consecutive cut to pensions, an increase in the retirement age and reductions to salaries, benefits and healthcare, the fury among Greece's population is growing.
Anais Metaxopolou, a 65-year-old pensioner demonstrating outside the Greek parliament, said: "They should go to hell and beyond.
"They should ask me how I feel when I have to go to church to beg for food."
Police have been deployed outside the parliament building in Athens. Larger demonstrations are expected on Wednesday when Greek MPs vote on a package which ministers say should save a total of 13.5bn euros (£11bn; $17bn).
Approving the tough reforms and passing the 2013 budget are key to receiving a 31.5bn-euro instalment from the International Monetary Fund and European Union that has been on hold for months.
The government must meet a 5bn-euro debt repayment in mid-November and says it needs the bailout cash to avoid going bankrupt.
However, the Democratic Left Party, which is the junior member of the three-party governing coalition, is refusing to back the package.
The second biggest coalition party, the socialist Pasok, is also facing a rebellion by some MPs.
Prime Minister Antonis Samaras hopes that even without the their support, he will have enough votes to get the austerity package through on Wednesday, and the budget on Sunday.
He has tried to reassure the public, who have endured repeated rounds of austerity and a five-year recession, that these would be "the last cuts in wages and pensions".
But Greeks have heard similar promises before, and Ilias Iliopoulos, head of public sector union ADEDY, said they had now had enough.
"We're calling on every lawmaker in parliament, without exception, and we're telling them that 100% of workers in the public sector are saying that they should not vote for these measures," he said.