Two young Chinese women undergoing sex-change surgery at a Shanghai hospital are hoping to be the first twins in the country to change their gender, a state-backed newspaper said.

The 25-year-old sisters from the southwestern province of Yunnan have already undergone preliminary surgery at a military hospital in the commercial hub, the Shanghai Daily reported.

"The operations on both the twins are successful," their surgeon, Zhao Yede, was quoted as saying.

"They said they would continue to save up (money) from hard work so they can return for their respective last phases of surgery," he said.

A spokesman for the People's Liberation Army Number 411 Hospital declined to comment to AFP, saying military units could not speak to foreign media.

The paper quoted one of the twins as saying they did not want any publicity, fearing they would lose their jobs.

The two sisters dress in male clothing, never wearing skirts or growing their hair long, the newspaper said. They both attended the same schools and university.

The hospital put them through medical and psychological tests before agreeing to perform the surgeries, it said.

Under Chinese law, their legal gender will remain female until they complete the surgical procedures and apply for a change to their status, the newspaper said.