Public sector workers in Greece are on strike against budget-cutting moves by the government.
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.
European Union leaders will discuss Greece's difficulties at a Brussels summit on Thursday, amid concerns the crisis could threaten the credibility of the euro.
The BBC reports European finance ministers are also due to hold a teleconference on Wednesday to talk about the issue.
On Tuesday, Prime Minister George Papandreou announced the government intends to raise the average retirement age from 61 to 63 by 2015.
A public sector salary freeze and a rise in petrol prices were announced last week.
Greece's deficit is 12.7% - more than four times higher than eurozone rules allow. The national debt is about 300 billion euros.
The BBC reports 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.