China's beach resort city, Sanya, is strengthening its ban on nude sunbathing and swimming on public beaches this month, but experts are calling for patients with psoriasis treating their diseases with sun to have their space.

Starting on Sunday, Sanya police took several measures to beef up the ban: increasing patrols on public beaches, passing out fliers to discourage people from naked sunbathing, and taking pictures of violators. High-definition surveillance cameras are also being installed.

Since Feb 8, nude sunbathing and swimming at public beaches has been forbidden. Violators will be detained for five to 10 days. So far, two people have been detained since the ban was imposed.

But, Zhou Xiaozheng, a sociologist at Renmin University of China who researches outdoor recreation in the country, said most nude sunbathers in Sanya are psoriasis patients.

"These people are not intentionally exposing their private parts. They need sunshine for medical treatment," Zhou said.

Shen Hong, a dermatologist at Hangzhou No 3 People's Hospital, said psoriasis is a chronic skin disease that is difficult to cure.

"For patients with psoriasis, red patches with scales will occur, especially on their scalp, ears and genitalia. Abundant sunshine and washing with seawater can relieve the pain caused by these patches," he said.

Sanya Mayor Wang Yong conceded that psoriasis patients are among the nude beachgoers in the city.

"There were dozens of patients with such skin disease when nude sunbathing started to appear in Sanya in 2002," he said. "They had notices from doctors, suggesting that they sunbathe for a certain amount of time. But we do not think this should take place in the city, especially when the group of patients has grown to the hundreds."

Wang said nude swimming and sunbathing is uncivilized behavior and may disturb other beachgoers.

Feng Qiankun, one of the patients, told Chengdu Business Daily that more than 400 psoriasis patients visit Sanya beaches during peak travel seasons. Most of them stay in Sanya from October to April.

Feng said if they do not sunbathe their private parts regularly, they will not be able to walk.

"We have tried to choose a remote place for naked sunbathing. If it were not for the disease, who would like to expose their private parts in public? Now that Sanya is conducting surveillance and exposing us, who is more uncivilized?" said Feng, as quoted by Chengdu Business Daily.

Fang Gang, an expert in sex and gender issues, thinks the local government should cordon off a space for skin-disease patients.

"Their behavior is not uncivilized. With nude sunbathing as their only way of improving their living standards, their rights should be respected," Fang said.

Mayor Wang said the city has no plans to set aside a certain area for psoriasis patients and naturists.