Surgeons in China today reported that they had successfully removed a third arm from a two-month old baby, after a pioneering operation which lasted for almost three hours.

Liu Jie-Jie astounded doctors and captivated the public when he was born with two left arms on April 1. Although neither was fully functional, both were equally developed and tests were unable to determine which was the stronger.

Dr Chen Bochang, of the Shanghai Children's Medical Centre, scoured library papers and internet databases unsuccessfully for similar cases. A decision was taken to remove the lower of the two arms, which had lain across the child's chest.

"The arm closest to the body was very bent and the hand was closed in a fist that could not be opened," said Dr Chen.

In a press conference following this morning's pioneering operation Dr Bochang said that the decision had proved to be correct. Nerves and blood vessels attached to the third arm were described as near perfect, allowing them to be removing by conventional amputation.

"The surgery really went much better and more smoothly than expected," he said.

The child, born to a farming couple from the rural Anhui province, has only one kidney and also suffers curvature of the spine. He cried when either one of his left arms was touched, but smiled and responded normally to other stimuli.

Dr Chen said that the baby would require long-term physical therapy to gain function in his remaining left hand, which has no palm and flexes in either direction."It will need a long time for the arm to recover and be like a normal arm. He may not be fully recovered until he is a teenager," he said.

The surgeon, who runs the centre's orthopaedics department, said that the case was so rare it was impossible to predict a prognosis. "We have virtually no information to go on," he said.

Jie-Jie's mother said she was relieved that the operation had been successful but worrried for her son’s future. "I’m very happy but there are some fears that I just can’t let go," she said.

The hospital paid for the surgery, which would otherwise have cost the parents 30,000 yuan (£2,000).

The cause of the baby's defect is unknown. It is generally accepted that additional limbs start out as limbs of a conjoined twin whose development never progressed. Environmental factors, such as pollution, have been ruled out because there is no clustering of cases.

There are no reliable figures for the frequency of such defects because many foetuses with more than four limbs are aborted or miscarried. In cases where the foetus survives, it is usually clear which limb is less developed and should be amputated. Jie-Jie’s case was especially rare because both left arms were almost equally well developed.

After the surgery, Jie-Jie made his first appearance for the cameras, asleep in his cot, his chest swathed in bandages.

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