The first word spoken by the recipient of the world's first partial face transplant after her successful operation on Sunday was a simple "Merci" (thank-you), her doctors said today.

Bernard Devauchelle, one of the lead doctors in the case, which has divided medical and ethical opinion in France and beyond, said that the 38-year-old patient spoke as she regained consciousness the day after her operation.

"There were no post-surgical problems," said Dr Devauchelle. "The patient was awake at the 24th hour and... her first word was ’Merci.'"

Dr Devauchelle was speaking at the first news conference since the operation, which was performed by a combined team of surgeons from the University Hospital in Amiens, northern France, and the University of Lyon.

Artists' images of the section of face that was transplanted - a single, irregularly-shaped piece of the donor's flesh that included the nose, lips, chin and surrounding flaps of cheek - were displayed to journalists.

The transplant was given to a woman who suffered severe facial injuries when she was mauled by a dog in May.

The operation has caused controversy, because doctors did not attempt reconstructive surgery before opting for the risky and psychologically-untested alternative of giving the patient much of someone else's face.

Dr Laurent Lantieri, a reconstructive surgeon and an adviser to France's National Consultative Ethics Committee, which sets voluntary guidelines for medical procedures, yesterday accused the transplant team of immediately seeking a donor face before attempting conventional surgery.

"The ethics committee said this kind of transplant should never be considered as an emergency procedure," said Dr Lantieri, who also questioned the psychological stability of the patient.

But today, Dr Devauchelle, his colleague, Professor Jean-Michel Dubernard, the pioneer of hand transplants, and the director of the University Hospital in Amiens, defended the operation and the unique circumstances of the patient.

"We are in an exceptional situation that required an exceptional response," said Philippe Domy, the director general of the hospital.

The involvement in the operation of Professor Dubernard, head of the Department of Transplantation Surgery at Lyons University Hospital, and the first surgeon to perform a hand transplant in 1998 and then a double forearm transplant in 2000, was seen as a vital help in gaining approval for the transplant.

Today Professor Dubernard acknowledged that he had initial doubts over the surgery. But he said that when he saw the extent of the woman’s disfigurement he "no longer hesitated for a second."

The doctors also denied French media reports that the patient was attacked by the dog after attempting to commit suicide. Professor Dubernard said the woman was attacked after taking a sleeping pill to calm down after a family argument.

"There was no suicide," said Professor Dubernard. He said that the woman, from Valenciennes, in northern France, was examined by several psychiatrists in the lead-up to the surgery and "all these teams gave the green light."

The chief medical risk facing the patient comes from the immuno-suppressant drugs that she will have to take to prevent rejection. The drugs will expose her to increased risks of infection, cancer and the possibility of liver and kidney failure.

The rejection rate for skin transplants is not known. For other organs, about 10 per cent are rejected in the first year after surgery. This can rise to between 30 and 50 per cent in the next 2-5 years depending on the organ. If the face transplant is rejected, it should be possible to remove it and try again.