Greece's government ordered a tax fraud inquiry Friday at one of the country's most visited archaeological sites, after tourists claimed its gift shop was not giving receipts for souvenirs bought there.

Inspectors sent to the world-famous Minoan ruins at Knossos on Crete this week found 534 breaches of the tax regulations in just one day, with the till at its shop left unplugged.

The debt-crippled country has struggled to combat a deeply ingrained culture of tax evasion, with many making little secret of their preference to do business in cash to avoid paying tax.

It's radical left-wing government, which is negotiating a third bailout from its creditors in five years, has vowed to crack down hard on fiscal fraud.

Culture Minister Nikos Xydakis warned of "zero tolerance" of public servants who fail to defend the interests of the state. "We await a report from the tax authorities before launching immediate disciplinary action," he said in a statement.

Tax inspectors swooped on Knossos, whose highly-decorated palace dates from 2,200 BC, on Wednesday, the news website TVXS reported, after complaints from tourists angry at not being given receipts.

Such scams to avoid paying VAT are so widespread that former finance minister Yanis Varoufakis floated the idea of wiring up an army of tourists to spy on shop owners and scare them into giving receipts to their customers.