Future Chinese astronauts must be close to perfection to meet the standards set for the men and women who will lead China into outer space.

They have to be scar-free from head to toe, have no history of serious illnesses and be unmarred by bad breath or dental cavities.

Officials from the No 454 Hospital of the People's Liberation Army in Nanjing, capital of Jiangsu province, said over the weekend they had already completed preliminary tests for such candidates to carry out the country's future space missions. The hospital is one of five medical institutions across the country conducting the second round of tests for its next batch of astronauts.

An employee of the No 454 Hospital who did not want to be named told China Daily Sunday about 100 hopefuls from the Nanjing Military Area, all of whom are fighter plane pilots with college degrees, are vying to become China's future astronauts.

These 100 candidates will also be put through about 100 tests that push them to their mental and physical limits before they can go to the next round.

The stringent requirements help ensure they will be able to deal with the tough, zero-gravity environment of space, said Shi Binbin, director of the department of air logistics at the No 454 Hospital.

"Scars on the body, for example, might burst and bleed when spaceships are accelerating," he said.

"The candidates who go through all the tests and meet all the requirements can really be called super-human beings," Shi said.

Yang Liwei, China's first spaceman and now the vice chief of the Beijing-based Aerospace Medical Engineering Institution, told reporters last month that China is planning to send female astronauts to space too, and that the selection is under way.