Greek drivers lined up for gas at the few stations still open Friday as a customs strike against government austerity measures left many pumps running dry.

The fuel shortage was the first serious consequence of growing labor protests against the Socialist government's emergency spending cuts program, aimed at easing the debt crisis in Greece and shoring up market confidence.

Customs workers have extended their strike against salary freezes and bonus cuts through next Wednesday, when unions across Greece will hold a general strike that is set to bring the country to a standstill.

European finance ministers have told Athens it must demonstrate signs of fiscal improvement by March 16 or it will be ordered to impose even tougher budget cuts. Greece has promised to slash its deficit from an estimated 12.7 percent of gross domestic product to 8.7 percent this year.

Finance Ministry officials say they are under EU pressure to ax the public servants' so-called "14th salary." Greek workers get their annual salary divided into 14 payments, with two of them given as holiday bonuses, in a measure originally designed to alleviate those with low incomes.

"We would consider cutting the 14th (salary) to be an act of war," said Yiannis Papagopoulos, leader of Greece's trade union umbrella group, the GSEE.

"The measures must be socially just. And this is something that we have not seen so far. They are generally aimed at wage-earners and pensioners, while business remains immune. It is finally time for those who for so many years gathered riches to pay up, invest, and help deal with the major problem at this time, which is unemployment."

The customs walkout has hampered imports and exports, but the supply of fuel has been the most affected. Gas stations around greater Athens were rationing fuel while stocks lasted. Traffic policemen were posted at some gas stations in Athens as cars queued for hundreds of meters (yards).

"We're out of regular unleaded, and now we're only selling diesel," said attendant Ioanna Antoniou at a gas station in the northern Athens suburb of Halandri. "There were a lot of cars lined up here earlier while we still had some unleaded left."

Antoniou said the gas station had rationed fuel to limit sales to euro20 ($27) per customer so they could serve more people.

Taxis also held a 24-hour strike Friday, protesting parts of the austerity package that increased fuel tax and will force them to issue receipts. Taxi drivers chanting "The measures mean unemployment" staged a noisy protest in central Athens that choked traffic.

"These measures won't do anything, all they will do is throw us out of work," cab driver Anastasis Damianidis said. "We can't become tax collectors — that's what they're trying to do. We will keep demonstrating."