Some 50,000 people are stranded in Greece, Tourism Minister Charis Theocharis told the broadcaster Skai on Monday, adding that steps are being taken in agreement with British authorities to bring them home.

"We will see 22,000 Thomas Cook clients leaving in the next few days," Theocharis said.

Nearly half of those stranded are in Crete, Greece's largest and southernmost island. Hotel owners there have been instructed to advise the guests not to rush to the airport, Skai said.

Greek hoteliers are worried about outstanding payments.

"There will be fall-out," Theocharis said, adding that his ministry is working on a plan to offset financial losses.

Thomas Cook filed for liquidation early on Monday, ceasing all trading with immediate effect in a move that will leave thousands of holidaymakers stranded.

"It is a magnitude-7 earthquake, and the tsunami is yet to come," the president of the tourist organisation on Crete, Michalis Vlatakis, told the To Proto Thema news outlet.

Thomas Cook had contracts with around 70 per cent of all hotels on Crete, Greece's largest island. Thomas Cook brought around 400,000 tourists to Crete this year alone, some 20,000 of whom are still there, Vlatakis said.

Still vulnerable after nearly a decade of a crippling financial crisis, bailouts and austerity reforms, Greece heavily depends on tourism, which generates 23 per cent of its gross domestic product.

Australian Associated Press