Tourism accounts for about 18 per cent of Greece's GDP and employs about a fifth of the Mediterranean country's workforce.

For decades Greece has been a magnet for European tourists, attracting 15 million or so visitors each year. How the sector fares this year will be critically important because the economy is already slowing after years of robust growth.

"Holiday bookings were down between 10 and 20 per cent during the Easter season," Andreas Andreadis, Head of the Hellenic Hotels Federation (HHF) said.

He said a 15 per cent drop in summer bookings was the most likely scenario but last-minute bookings could bring the figure to 10 per cent.

"Greece will be considered a winner if it manages to contain losses to 10 per cent," he said.

Previous estimates from other tourist bodies saw summer bookings, mainly from Britain and Germany, Greece's top two tourist markets, falling by as much as 17 per cent.

The global economic downturn is seen as one of the reasons for people staying away, but tourism has also being dented by recent outbreaks of violence in the capital.

International media carried extensive coverage of riots that shook the country in December after a police officer fatally shot a teenager, igniting discontent against a backdrop of high youth unemployment.

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