One of a pair of Nepali twins once joined at the head died on Tuesday, seven years after surgeons in Singapore separated their fused skulls, a doctor said.

The twin girls, Ganga and Jamuna, 7, had been living in Nepal with their parents since their surgery hit international headlines in 2001.

But Basanta Pant, a neurosurgeon at Kathmandu Model Hospital, where the girls undergo regular medical check ups, said Ganga died in hospital while being treated for a chest infection.

"We ventilated the girl for two days. But eventually she passed away because of a chest problem," Pant told Reuters.

Pant said Ganga had been the weaker of the two since the surgery but Jamuna was doing well.

Doctors at the Singapore General Hospital donated their services for the delicate four-day operation to separate the twins' fused skulls and intertwined brains.

Donations from the public paid for the other costs, that had been beyond the reach of their poor family from the Himalayan foothills in west Nepal.

Twins fused at the head are rare, occurring once in every two million live births. Successful separation is even rarer.

Another pair of twins, Iranian sisters Laleh and Ladan Bijani, 29, who were also joined at the head, died on the operating table in Singapore in 2003, as a team of doctors attempted to separate them.