Authorities in Japan are urging foreign visitors to stop illegally defacing a series of giant, ancient sand dunes in the south west of the country after an increase in graffiti.

Defacing the Tottori dunes by drawing in the sand has been illegal for 10 years, but many overseas tourists misunderstand the site's rules, according to The Mainichi.

In January, a foreign couple wrote "Happy Birthday Natalie" across a dune.

Officials have added signs in English, Chinese, and Korean to make sure all visitors know the rules.

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Authorities in Japan are urging foreign visitors to stop illegally defacing a series of giant, ancient sand dunes in the south west of the country after an increase in graffiti drawn in the sand.

The government has seen an increase in visitors drawing "graffiti" into the sand at the coastal dunes in Tottori county, around 120 miles from Osaka, and 400 miles from Tokyo.

228 such incidents were recorded by the government last year, up from 200 drawings in 2017, English-language Japanese newspaper The Mainichi reported.

Defacing the dunes has been illegal for 10 years, the paper said, but visitors are seemingly unaware of the rules.

In April, officials had to clean up drawings of the name "Sebastian" and a face, the newspaper reported.

Earlier this year, a foreign man and woman wrote "Happy Birthday Natalie" across a dune. They were ordered to clean the area themselves.

Authorities say "sand graffiti" has been on the rise as more overseas tourists come to Tottori, and misunderstand the site rules, The Mainichi said.

Japan welcomed more than 31 million foreign visitors last year, according to its National Tourism Organization. That is more than triple the number of tourists that came from abroad in 2008.

With their ever-changing landscapes and wave patterns, the Tottori Sand Dunes have proven to be an especially popular destination among tourists seeking a good Instagram picture. The dunes have existed for over 100,000 years, and stretch around 10 miles along the coast.

People enjoy Pokemon Go during the Pokemon GO Safari Zone at Tottori Sand Dune on November 24, 2017 in Tottori, Japan. Getty Images

Officials have added signs in English, Chinese, and Korean to the dunes' entrances make sure all tourists know not to draw in the sand. But they are worried these changes might not be wide-reaching enough.

Tomihisa Ikeuchi, who works with the government's natural green resources division, told The Mainichi most of the park's employees only speak Japanese, and cannot explain the policy to foreigners.

"We are concerned about whether the rules are fully understood, but we want to continue to protect views of the beautiful sand dunes," he said.

Read more: A Japanese city has put up signs asking tourists not to eat while they walk around

The dunes' multilingual signage is part of a growing trend in Japan.

The seaside city Kamakura and Kyoto's Nishiki Market have put up signs asking visitors not to eat while walking around. The request is meant to encourage good manners and avoid littering.