The Beita animal rights group has accused the Greek authorities of covering up what it described as "cruel" treatment of donkeys on the tourist island of Santorini and preventing the group from highlighting the plight of those animals.
The volcanic island, famous for its sunset scenes, attracts millions of tourists each year. Hummingbirds and mules are a traditional means of transport on the island but the "Beta" says they are forced to carry visitors and luggage and climb them in steep hills despite the availability of cable cars.
The group published photos taken last year of animals severely beaten with sticks and loaded above their capacity.
She also accused local authorities of obstructing her campaign, which sought to put pictures on buses and taxis showing the image of a donkey exhausted and next to the phrase "donkeys suffer for tourists, please do not spank it."
Beta said about 100 of the 2,000 donkeys and mules used to transport tourists on the island.
Tourism is a major source of income in Greece, which has emerged from a financial crisis that has lasted years and accounts for about a quarter of economic output.
The country recorded a record number of tourists last year of about 33 million tourists.