BEIJING (Reuters) - China has warned image-conscious citizens against using the rack to lengthen their legs after several such operations went badly wrong, Xinhua news agency said.

Ten people were reported to have been disfigured after they underwent stretching surgery last year, it added.

The operation, which involves breaking the patient's legs and then stretching them on a rack, has become popular among young professionals "desperate to climb up the ladder in the country's height-conscious society", Xinhua said, without trying to pull anyone's leg.

"Leg-lengthening surgery is a clinical orthopaedic treatment, not cosmetic surgery," ministry spokesman Mao Qunan was quoted as saying.

"Leg-lengthening surgery must only be carried out for strict medical reasons and performed in authorised hospitals."

State media have said profit-obsessed small clinics sold the operation hardest to increasingly wealthy Chinese in the cities, who have taken to cosmetic surgery such as breast enlargements with enthusiasm.

Height is usually listed as a requirement for jobs or certain schools in China. Many employers require women to be over 1.65 metres (5 ft 5 in) and men over 1.70 metres.

It is also an important factor in courting, when many Chinese women expect their partners to be over 1.70 metres and men also care about their potential wives' height to avoid short offspring.

As a result, calcium supplements and other "height-enhancing" medicines are always among the best sellers at Chinese pharmacies.

"It is very risky for healthy people who only complain about being short," Mao was quoted by Health News as saying of the operation.