"A woman gave birth this morning to Siamese twins joined at the stomach and pelvis," Gaza's Shifa Hospital head of neonatal unit Allam Abu Hamda told AFP.
Dr Abu Hamda said the girls' complicated condition "cannot be dealt with in the Gaza Strip, so we hope they will be transferred abroad for a separation".
An uncle who preferred not to be named said: "We hope they can leave to do what is necessary for their rare conditions."
Conjoined twins that share key organs have low chances of survival.
The twins, whose condition Dr Abu Hamda said was stable, have one shared leg, but separate hearts and lungs.
Israel has maintained a blockade of the enclave for a decade, citing security fears over Gaza's Islamist rulers Hamas.
In 2010 conjoined twins from Gaza were transferred to Saudi Arabia for surgery to separate them, but doctors in Riyadh said their condition was too delicate to operate and they died.
Conjoined twins born in Gaza in November 2016 later died.