Conjoined female twins born at the Nelson Mandela Academic Hospital in Mthatha cannot be separated, the Eastern Cape Health Department said on Friday.

"The babies share a heart, which only has two chambers, as well as a liver and pancreas," spokesman Sizwe Kupelo said.

"A doctor was flown in today to check on their status and this is what was found...they also have kidney problems and will not be separated."

The girls' mother, Bongiswani Tumela from Libode near Mthatha, gave birth to the babies on Wednesday at about 7pm with a combined weight of 800 grams.

The girls are joined at the chest, and were currently dependent on oxygen, Kupelo said.

According to reports Tumela only learnt she was carrying twins after an ultrasound scan at the hospital after she had been admitted.

Kupelo said the department would pay for the tests and operations.

"They will remain in hospital for now, and we will keep the public updated on their conditions," he said.