Greek riot police had to use tear gas to clear striking staff blockading the Acropolis today.

Up to 100 Culture Ministry workers shut down the country's most famous ancient site yesterday complaining they were owed up to 22 months back pay.

They barricaded themselves inside, padlocked the entrance gates and refused to allow any tourists in until their demands were met.

Police in riot gear went in today after a court said the protesters were hindering access to the ancient site and its 2,500-year-old marble temples.

"Riot police and violence won't break the strike," the protesters chanted, clinging to the entrance gates.

But police broke in through a side entrance then used pepper spray to clear the protesters from the main gate.

Dozens of bemused tourists who had arrived to visit the site looked on as the stand-off unfolded.

"We know the workers have a right to protest, but it is not fair that people who come from all over the world to see the Acropolis should be prevented from getting in," said Spanish tourist Ainhoa Garcia shortly before the clashes broke out.

Greece is in the middle of a tough austerity program which has cut public workers' salaries and trimmed pensions in an effort to pull the country out of a severe debt crisis. The austerity plan has led to a series of strikes and demonstrations as workers' unions protest the cutbacks.

Guards and workers at archaeological sites have long been complaining they are owed months of back pay, and have shut down the Acropolis before in protest, though usually only for a few hours at a time.

But authorities often are sensitive to protests at the emblematic ancient site, particularly as the country largely relies on tourism for revenue.

And visitors who have travelled from far-flung countries were unimpressed by the protest.

"We think this is a shame. We will not recommend that people come to Greece," said Veronica Traverso, a tourist from Argentina standing with a friend outside the padlocked gates. "We are not to blame for Greece's troubles."