The 72-hour strike by customs officials to protest salary freezes and bonus cuts, which began Tuesday, has been extended until Feb. 24.

The walkout has forced the closing of half a dozen customs border points in northern Greece and hampered imports and exports.

Many petrol stations in Athens reported to have run out of all fuel, while others that were still operating were rationing the amount of gas allotted to each driver.

Last week, a civil servant strike grounded flights, shut down schools and government services, including hospitals, in a 24-hour protest. A larger, general strike is planned by public and private sector employees for Feb. 24.

Taxi drivers also held a 24-hour walkout Friday, protesting the government's austerity measures that have increased fuel tax and forcing them to issue passengers receipts.

Employees are striking over cutbacks which include a freezing of civil servants' salaries, cuts in bonuses, a two-year increase in the average retirement age and higher taxes.

Greece is facing massive pressure from European Union partners to adopt new deficit-trimming measures by March.

Greece won approval for an austerity program that foresees a deficit reduction from 12.7 percent of gross domestic product (GDP) in 2009 to the 3-per-cent limit recommended by the EU by 2012, with a massive 4 percentage point cut envisaged this year.

In exchange, euro zone and EU ministers extracted a promise from Athens to present further belt-tightening measures by March 15, when Greece is expected to produce the first of a series of monthly reports to the European Commission on the state of its public finances.

Greece will also explain in a letter being sent by the Finance Ministry to the European Union on Friday how it used a currency swap deal with United States investment bank Goldman Sachs that apparently helped it to mask the size of its budget shortfall.

In Athens, the country's two largest parties disagreed over plans by the Socialist government to set up a parliamentary inquiry into the alleged misreporting of financial data that triggered the crisis.

The financial difficulties faced by Athens have plunged the euro area into the most serious crisis since it was created 11 years ago, throwing other financially precarious countries such as Spain and Portugal under the spotlight of financial markets.

Meanwhile, France has 10 to 20 days of fuel supplies to cope with a worsening refinery strike, the French Petroleum Industry Body (UFIP) said, ruling out an imminent petrol shortage as Parisians head off for their winter holiday.

Workers at Total's six French refineries extended their three-day strike on Friday and the CGT union said some petrol stations could run out of fuel as soon as this weekend.

But Jean-Louis Schilansky, head of the UFIP, told Reuters in an interview, there was no short-term risk of fuel supply in France due to the refinery strike.

"We have 160 fuel storage sites spread over the country which continue to supply petrol stations," Schilansky said.

"While some localized shortages are possible this should remain minimal," he added.

Total, which owns six refineries out of 12 and 31 fuel storage sites out of 160, said 7 fuel sites were on strike.

The CGT union at ExxonMobil's two French oil refineries called on workers to down tools on Feb. 22 in support of their striking Total colleagues, two union officials said.

"Whether it will happen or not is up to the workers," a union official at the 115,000 barrel-per-day (bpd) Fos-sur-Mer refinery in southeastern France told Reuters by telephone.

Exxon's Port-Jerome refinery has a 240,000 bpd capacity.

Workers are protesting over the possible permanent closure of Total's Dunkirk plant in northern France, hit by low margins and poor demand - a problem besetting many European refiners.

Strikers, who want Europe's largest refiner to restart production at Dunkirk after Total stopped output in September, are in the process of halting production at the group's five other refineries, union officials said.

"We are going toward a fuel shortage if Total and the government don't react," the CGT union coordinator for Total told Reuters TV on Friday.

Strikers have been preventing crude and fuel products from entering or leaving Total's six refineries by truck, train, barge, pipeline or ship for the last three days.

The French Industry Minister Christian Estrosi, who talked with Total's Chief Executive Christophe de Margerie early on Friday, said in a statement that Total had to reassure refinery workers very quickly.

A Total spokesman told Reuters no other French refinery should be concerned by a restructuring project.

Total will hold an extraordinary meeting on March 29 to decide on the future of the 137,000 barrels-per-day (bpd) Dunkirk plant.

Total has put off a decision on whether to close Dunkirk from Feb. 1 - a move analysts said aimed to avoid embarrassing the government before regional elections on March 14-21.

"What we want is that Total brings forward an extraordinary meeting over Dunkirk to next week," one union official said.

Total said no redundancies would take place if Dunkirk was closed and workers would either be offered other jobs in the group or be given early retirement.

Total has been struggling for several years with its European refining and has vowed to cut production capacity by 500,000 bpd between 2007 and 2011.

If Total decides to close Dunkirk, the group will still need to cut another 150,000-170,000 bpd in capacity to meet its target, according to Reuters' calculations.