Doctors in Allahabad city of India's northern Uttar Pradesh state have successfully separated day-old conjoined twins through surgery.

The infants have been kept in intensive care unit.

A team of seven doctors, specialising in various aspects of anatomy operated on the twins on Sunday, who shared some common organs.

"Some parts of their body were joined. They had a common liver, some common intestines, which needed to be separated. They had separate hearts, which were joined by thick veins, this was most challenging aspect of the operation," said Dinesh Agrahari, a surgeon.

Conjoined twins occur roughly once in every 50,000 births and few are born alive or live long.

For twins who undergo surgery, one or both often die after the operation, and the rate of survival beyond the age of two is just 20 per cent.