A 24-hour general strike is under way in Greece in protest at the nation's austerity measures.
Flights and ferry services have been cancelled, schools, government offices and tourist sites closed, and hospitals are working with reduced staff.
At least 16,000 people have joined protests organised by the main unions in central Athens.
The European Commission is discussing ways of propping up banks in Europe to protect them from the Greek crisis.
Meanwhile, in its latest report on the European economy, the International Monetary Fund (IMF) has warned that economic growth is in danger of petering out and a global recession in the coming year cannot be ruled out.
End Quote Dimitris Kizilis Protester
We believe, as workers, that patriotism is to respond with actions”
Global financial markets have been in turmoil over fears that Greece could default on its debt, most of which is held by European banks. In other developments:
- On Tuesday, Moody's ratings agency slashed Italy's credit rating from Aa2 to A2, blaming an overall loss in confidence in eurozone governments.
- Despite the Italian downgrade, European markets rose sharply as trading opened on Wednesday.
- Belgium and France are working on plans to rescue the Franco-Belgian Dexia bank, which is exposed to Greek debt.
The general strike is the first since the Greek government announced an emergency property tax and the suspension of 30,000 public sector staff last month.'Lives ruined'
The government says the stringent austerity measures cannot be avoided if the country is to reduce its deficit of 8.5%, a key requirement in securing a second instalment of bailout cash pledged by the EU.
At the scene
It is a very noisy demonstration indeed here, certainly the biggest demonstration by Greece's public sector in several weeks. The country has ground to a halt.
All of these people are extremely angry at the austerity measures that the government is desperately trying to push through to qualify for the next instalment of its international bailout, in order to stave off bankruptcy and avoid defaulting on its debts.
The government says it is in a very difficult position, because it must pursue its austerity drive to meet its fiscal targets and reduce the budget deficit to avoid bankruptcy within the next few weeks.
But this wave of social unrest is growing by people who say the measures are deepening the recession, stagnating the economy and stunting Greece's growth.
But the measures are hugely unpopular and have led to a wave of strikes and protests.
Tens of thousands of people have stayed away from work across Greece, including air traffic controllers, tax workers, teachers, hospital staff, public transport workers, police and other emergency workers.
Thousands of people have gathered in central Athens to march towards Syntagma Square and stage a demonstration outside parliament. Protests were also planned for other cities.
Police have fired tear gas at small groups of protesters who were throwing stones.
Critics of the austerity drive say it is deepening the recession, stunting Greece's growth - the economy will shrink 5.5% this year - and stopping Greece from being able to reduce its government debt itself.
Protesters also say they are unfairly bearing the burden of the country's debt.
"This is an opportunity for the Greek people, whether in the public or in the private sector, to fight this, to deny this logic that we must bow our heads all the time to save the country and show patriotism," said 37-year-old protester Dimitris Kizilis.
"We believe, as workers, that patriotism is to respond with actions."
Stathis Anestis, a spokesman for Greece's main union GSEE, said the new measures were "just extending the unfair and barbaric policies which suck dry workers' rights and revenues and push the economy deeper into recession and debt".
"With this strike, the government, the EU and the IMF will be forced to reconsider these disastrous policies," he told Reuters.
Greek civil servant and trade unionist Tiana Andreou told the BBC that people's lives had been ruined.
"We have decided that we're going to stop this."
Some militant civil servants are promising to sabotage the moves. On Tuesday, protesters again blocked the entrance to several government departments including the finance and transport ministries.
The government says it has enough cash to pay pensions, salaries and bondholders until mid-November, having previously said it needed more money by mid-October to avoid a default.
Inspectors from the IMF, European Central Bank and European Commission - known collectively as the troika - have been in Greece this week to assess its financial situation.
But eurozone finance ministers have delayed a decision on handing over the money, after Greece said it would not meet this year's deficit-cutting plan.
The government admitted that the budget deficit will stand at 8.5% this year, rather than the 7.5% target.
On Wednesday, the IMF's European chief Antonio Borges said there was no rush for the second bailout, and that he was "confident negotiations will come to a positive conclusion".