OSAKA -- A 35-year-old man from Tokyo died several hours after undergoing a sex-change operation in February at an Osaka clinic suspected of malpractice, sources close to the case said Tuesday.

The man, a company employee who lived in Koganei, western Tokyo, had suffered from a sexual-identity disorder and underwent the operation at Wada Keisei Clinic in Osaka's Kita Ward on Feb. 25.

The five-hour operation began at 6:40 p.m. His condition deteriorated shortly afterward and he was taken to another hospital, where he was pronounced dead at around 6:35 a.m. the next day, the sources said.