Thailand's Health Ministry ordered hospitals and medical clinics to temporarily stop performing castrations for non-medical reasons, saying Wednesday that the procedure performed on transsexuals needs stricter monitoring.

A letter will be sent to medical facilities around the country telling them to halt so-called commercial castrations until further notice, he said. Violators could face closure of their practices.

"As of today, doctors can perform the surgery if there is a medical reason to do so - not for any other reason," ministry spokesman Suphan Srithamma said.

The move came after a leading gay activist, Natee Teerarojjanapongs, called on the Medical Council to take action against clinics that perform castrations on underage boys.

Natee, head of the Gay Political Group of Thailand, said he received several complaints from parents of underage boys seeking castrations in part because of Internet advertisements that promise cheap operations resulting in feminine qualities such as softer skin.

Suphan said he did not have official statistics on the numbers of castrations performed in Thailand, but said many underage patients were unaware of the risks it posed, including hormonal imbalances and stunted physical development.

The ministry and the Medical Council of Thailand will draft new guidelines that doctors must follow before carrying out the procedure, Suphan said.

Existing rules require boys under age 18 to have parental consent before undergoing castration but it is suspected that many doctors overlook the rule, Suphan said.

"It's a totally wrong perception that castration will make boys more feminine," Natee told The Bangkok Post last week. "These youngsters should wait until they are mature enough to thoroughly consider the pros and cons of such an operation."

Dr. Thep Vechavisit, owner of the Pratunam Polyclinic in Bangkok, which specializes in sex change surgery, said the surgery was a better option than taking excessive female hormones, which can cause liver damage. Many many young male transsexuals take hormones, he said.

His clinic charges $125 for non-medical castrations and has performed 205, mostly for Thais, since first offering the service in 2004, he said.

"There's nothing wrong with this procedure," Thep said.