Woo-Suk Hwang and his team of researchers at Seoul National University made world headlines earlier this year when they created stem cells with a patient's specific genetic material, derived through cloned embryos.

Now they have cemented their place as leaders in the field by creating Snuppy, the first dog cloned from adult cells by somatic nuclear cell transfer. This is the same technique used to create Dolly the sheep, the world's first cloned mammal, and other animals.

Hwang said the breakthrough in cloning dogs may advance work on combating diseases by therapeutic cloning with stem cells.

"Our research goal is to produce cloned dogs for [studying] the disease models, not only for humans, but also for animals," Hwang said.

Snuppy, short for for Seoul National University puppy, where Hwang's lab is located, is a male born by caesarean section weighing 530 grams on 24 April after a normal, full-term pregnancy in a yellow Labrador surrogate mother.

A second puppy, NT-2, weighed in at 550 grams but died 22 days later from pneumonia. A post-mortem exam showed there were no anatomical problems with the dog that died.

A total of 1095 reconstructed embryos were transferred into 123 surrogates to create the two dogs - an efficiency rate of 1.6%.

Both puppies were created from an adult skin cell taken from a male Afghan hound using somatic cell nuclear transfer.

Sheep, mice, cows, goats, pigs, rabbits, cats, a mule and horse have been cloned in the same way.

The Afghan breed was selected mainly for its size and striking appearance, researchers said.

Research purposes only

"The purpose of this research is to produce research animals, not domestic pets," the research team said in a statement.

"Techniques that advance our understanding of diseases and their therapy are to be encouraged but cloning of animals raises many ethical and moral issues that have still to be properly debated within the profession"

Freda Scott-Park, president-elect of British Veterinary Association

They said the difficulty in producing dog clones "underscores the importance of responsible regulation of this vital science".

The scientists believe the ability to clone dogs will help to determine environmental and genetic contributions to traits of different breeds and could also help preserve rare species.

Scientist Gerald Schatten, who participated in the study, said cloning dogs may help scientists study diseases that affect dogs as well as humans such as cancer and diabetes.

Therapeutic cloning involves creating embryos for a supply of stem cells to be used for research or therapy to develop cures diseases ranging from diabetes to Parkinson. Stem cells are master cells that can be coaxed to develop in any cell tissue type in the body.

Some scientists cautioned there are many unresolved ethical questions about where the science may lead.

"Techniques that advance our understanding of diseases and their therapy are to be encouraged but cloning of animals raises many ethical and moral issues that have still to be properly debated within the profession," Freda Scott-Park, president-elect of the British Veterinary Association said in a statement.