Scientists have received the news that a human embryo has been cloned into a woman with a large dose of skepticism and are challenging the maverick fertility expert to prove it.  

US-based Dr. Panos Zavos said on Sunday some secrecy had to be maintained in his work and he stood by his announcement that he had transplanted the embryo into a 35-year-old-woman less than two weeks ago.

The claim bore a striking resemblance to an announcement made last year by the Raelian Movement -- a cult that believes life on Earth was engineered by visitors from outer space -- saying it had produced the world's first cloned human.

It never came up with any scientific evidence but managed to whip up huge publicity around the world.

Scientists are now throwing down a similar gauntlet to Zavos, urging him to publish his results so they can be reviewed by experts.

"Like most scientists and doctors I remain extremely skeptical of the claims," said Bob Ward from the Royal Society, Britain's main academy of science.

Zavos told BBC radio he had worked in the reproductive arena for 25 years or more and had "delivered everything that he said that he would."

"We have to maintain some secrecy in our work," Zavos said. "Why? Because a lot of people would like to know where we are, what we do and reveal everything."

Skeptics point to similar claims, like the Raelian Movement, that have fizzled out as no evidence has been forthcoming.

Italian fertility doctor Severino Antinori, a former colleague of Zavos, said nearly two years ago that three women were pregnant with clones. He too produced no evidence but became a household name in Italy following his claims.

Peter Braude, a fertility expert at King's College London said: "Zavos does not represent mainstream science and what and his colleagues are doing is seeking publicity rather than advancing science."

"It is highly unlikely that he has successfully made a cloned human embryo," Professor Chris Higgins of Britain's Medical Research Council said of Zavos. "So far he has produced no data at all."

Even Zavos admitted the chances of the woman's pregnancy going to term were slim. He said he would continue until he was successful and was looking for more volunteers.

British Health Secretary John Reid denounced the claim and pointed out that cloning a child was illegal in Britain, while the Vatican condemned it as immoral.

Last October, Zavos said he was only weeks away from implanting a cloned embryo in a surrogate mother but leading fertility experts dismissed the claim.

(China Daily January 19, 2004)