Greeks strike over austerity plan
Public sector workers in Greece have launched a national strike, with thousands rallying against the government's budget-cutting measures.
Flights have been grounded, many schools are closed and hospitals are operating an emergency-only service.
The government wants to freeze pay, gather more taxes and reform pensions.
EU leaders will discuss Greece's difficulties at a Brussels summit on Thursday amid concern the crisis could threaten the credibility of the euro.
European finance ministers are also due to hold a teleconference on Wednesday to talk about the issue.
Despite heavy rain, there were rallies across Greece on Wednesday, with thousands of striking workers and pensioners gathering in Athens.
Several thousand people were also reported to have protested in Greece's second city, Thessaloniki.
The rallies have been mainly peaceful, but in one incident police fired tear gas at rubbish collectors who tried to drive through a police cordon.
“ It's a war against workers and we will answer with war ”
Union member Christos Katsiotis
Some demonstrators threw stones at the police but the trouble was quickly defused.
The unions regard the austerity programme as a declaration of war against the working and middle classes, the BBC's Malcolm Brabant reports from the capital, and their resolve is strengthened by their belief that this crisis has been engineered by external forces, such as international speculators and European central bankers.
"It's a war against workers and we will answer with war, with constant struggles until this policy is overturned," said Christos Katsiotis, a union member affiliated to the Communist Party, at the Athens rally.
Others in the capital either see the cuts as necessary or argue that the strike is politically motivated. Have Your Say
"We have to implement the austerity measures, or the country will not be able to get out of this crisis," said Katerina, a private sector employee. "We have to pay for the mistakes of the past."
On Tuesday, Greek Prime Minister George Papandreou's socialist government announced that it intends to raise the average retirement age from 61 to 63 by 2015 in a bid to save the cash-strapped pensions system.
The move comes on top of other planned austerity measures, including a public sector salary freeze and a hike in petrol prices announced last week.
Deficit and debt
Further government measures include the non-replacement of departing civil servants, and tax collectors recovering billions of euros lost to tax evasion.
Mr Papandreou has already faced down a three-week protest by farmers demanding higher government subsidies.
Public sector workers will not be hit as hard as they have been in the Irish Republic, but they complain that some of the lowest paid will suffer while the rich dodge tax with impunity, says BBC Europe correspondent Jonny Dymond.
Financial markets around the world and politicians from across Europe will be watching the situation carefully, he reports from Athens.
Greece's deficit is, at 12.7%, more than four times higher than eurozone rules allow. Its debt is about 300bn euros ($419bn; £259bn).
The markets remain sceptical that Greece will be able to pay its debts and many investors believe the country will have to be bailed out.
The uncertainty has recently buffeted the euro and the problems have extended to Spain and Portugal, which are also struggling with their deficits.
The possibility of Greece or one of the other stricken countries being unable to pay its debts - and either needing an EU bailout or having to abandon the euro - has been called the biggest threat yet to the single currency.
Ahead of Thursday's Brussels summit, some business media reported that Germany is preparing to lead a possible bail-out, supported by France and other eurozone members.
Mr Papandreou was in Paris on Wednesday for talks with President Nicolas Sarkozy.