Athens, Greece (CNN) -- The Greek capital was tense Thursday after the government ordered truck drivers back to work following a three-day strike.
Striking workers threw rocks and plastic bottles at the gates of the transport ministry in the morning, and police used tear gas to disperse the angry crowd.
The strike has caused gas stations in Athens to run out of fuel, stranding people around the country just as many Greeks leave for August vacation.
Bookings by tourists from neighboring countries were also "frozen" because of the strike, the head of the Hellenic Hotels Federation, Andreas Andreadis, said in a television interview Thursday.
Thousands of tourists from Russia, Bulgaria, and Serbia, who are traveling by car, remain stranded in northern Greece because of the strike, Andreadis said.
Many gas stations have signs saying they are out of fuel, and there are long lines at those stations that still have supplies.
The government issued a rare emergency order to the owners and drivers of the trucks to return to work Thursday, saying they face severe penalties -- including having their licenses revoked -- if they don't.
Greece has about 33,000 licensed truck drivers. They went on strike this week to protest government plans to open up their industry and issue new licenses.
The government is required to make the changes under the terms of loan packages from the European Union and International Monetary Fund.
From Journalist Elinda Labropoulou