The parents of four-year-old twins who were separated after 26 hours of surgery said they were overwhelmed by their reunion with their daughters.

A day after the operation, Jake and Erin Herrin said it was like seeing Kendra and Maliyah "born again".

Speaking at a news conference at the Primary Children's Medical Centre in Salt Lake City on Wednesday, Mr Herrin said: "They were in brand new bodies. It was really an amazing experience."

The twins are in critical condition and nurses have said their vital signs continued to mirror each other, as if they were still conjoined.

"They are doing extremely well," said Dr Rebecka Meyers, co-ordinator of the separation, which began on Monday morning and concluded on Tuesday.

Kendra and Maliyah were joined at mid-torso, with some shared organs and just two legs. Doctors divided the twins' shared liver, bladder and a portion of their large intestines, and split and reconstructed their single pelvis.

Each girl kept one leg, and Kendra was left with the kidney they had shared. Maliyah was to begin kidney dialysis in preparation for receiving a kidney from her mother in three to six months.

Doctors expect the girls will need reconstructive surgeries to help fit them with prosthetic legs.

"These girls will never be girls who did not undergo a major separation and have special battles and special needs," Dr Meyers said. "But they will be able to live very good, fulfilling lives."