A Chinese man has locked himself inside a hospital in China's southwest Yunnan Province ans has refused to leave after accusing medical staff of tattooing his right buttock while he was unconscious during a surgery.

The 34-year-old Sheng Xianhui claims that the Chinese characters, which translates as "Stone Disease," was tattooed on his backside by medical staff Yunnan Stone Disease Hospital after he had undergone a gall stones removal there.

But the hospital denies the charge and had called in the police to intervene and force Sheng out. Sheng, naturally welcomed the police.

"I'm not leaving. I'm worried that if I go out for even half an hour, the hospital will claim I had the tattoo done outside. But even if I wanted a tattoo, I wouldn't want those characters and I wouldn't want it on that part of my body," he said.

Sheng added that he learned of the tattoo when he was alerted by his wife Hu Juan who noticed the Chinese characters when he took a shower at the hospital one week after the operation.

"After the surgery, I felt my right buttock was painful. However I thought it was a normal reaction after the surgery," he said.

And Hu added: "We came here on a friend's recommendation, but never expected they would engrave characters on my husband's ass."

The hospital claims the tattoo may be caused by an allergic reaction to the hospital's bed sheet.