THE first monkeys cloned in the same way as Dolly the sheep have been born, raising concerns that it may soon be possible to clone humans.

Chinese scientists have announced the births of Zhong Zhong and Hua Hua, a pair of healthy macaques that are genetically identical.

The infants are being bottle-fed and are said to be growing normally compared with monkeys their age. More cloned births are expected this year.

Previously scientists have “cloned” primates by splitting an embryo in half, but the process is essentially artificial twinning rather than true cloning.

Researchers said they were hoping it would allow the creation of large numbers of genetically uniform monkeys, which could be used in labs to improve research.

The study was greeted with mixed opinions from scientists and ethics charities.

Darren Griffin, professor of genetics at the University of Kent, said: “The first report of cloning of a non-human primate will undoubtedly raise a series of ethical concerns, with critics evoking the slippery slope argument of this being one step closer to human cloning.”

The Scottish Council on Human Bioethics warned the research “opens the door” to human cloning.

Callum MacKellar, the council’s director of research, said: “There is a very serious risk that human clones would just be created to fulfil the desires of their creators. Humans should never be brought into existence to just replace a person who already exists or who has died because some parents want a copy of a famous or desirable person.

“Children should be created for themselves no matter who they are.”

Human cloning is banned under international law.

In their experiments, Chinese scientists took donor eggs from monkeys and removed the nucleus before adding tissue cells from a macaque foetus and implanting them into a surrogate.

Although Zhong Zhong and Hua Hua are genetically identical, having received DNA from the same monkey, they were born two weeks apart to different surrogate mothers.

The same technique was used by the Roslin Institute in Edinburgh to create Dolly the sheep in 1996, the first mammal to be cloned.

Until now, attempts to carry out the same process in primates have proved difficult because of the far more complicated process of cell division and early development.

The Chinese team solved the problem by switching on and off certain genes that were preventing the embryos from forming properly.

The scientists say they plan to continue improving the technique.

The research was published in the journal Cell.