China is disputing a report by U.S. and Hong Kong researchers last week that says a new vaccine-resistant strain of bird flu virus has appeared in southern China. Meanwhile, the World Health Organization says China has agreed to hand over bird flu virus samples that WHO scientists have been requesting since last year.

Chinese officials on Friday expressed anger at any suggestion that Beijing has been covering up the appearance of a new strain of the bird flu virus.

A U.S. publication, the Proceedings of the National Academy of Sciences, last week published a report by American and Hong Kong researchers that said a vaccine-resistant strain - identified as the "Fujian strain" - had been found in poultry outbreaks in southern China, and also appeared in Hong Kong, Laos, Malaysia and Thailand.

China's top veterinarian, Jia Youling, head of the Veterinary Bureau at the Ministry of Agriculture, strongly disputed the findings to reporters in Beijing Friday.

"There is no such new Fujian-like virus variant at all," said Jia. "It is utterly groundless to assert the outbreak of bird flu in Southeast Asian countries was caused by avian influenza in China."

The World Health Organization's representative in China, Dr. Henk Bekedam, said a much wider study is necessary to know whether a new strain exists.

"The discussion about [what is] new or not new needs to be done by scientists," he said. "This is a very specific, specialized area, and, to come to a conclusion, I really think you need to get all the global experts together, and then to agree if it's new or not."

Dr. Bekedam on Friday said the Chinese Ministry of Agriculture had assured his office it has finally shipped 20 bird flu virus samples from 2004 and 2005 that the WHO has been requesting since last year. He says scientists need to see the samples, so they can watch for virus mutations and start developing new vaccines.

"Today, we are very hopeful. Today, those virus [samples] are being shipped," he said. "We hope as well tomorrow to start discussing about the viruses, which are also the viruses of 2006 to be shared."

Currently, the H5N1 strain of bird flu is the dominant virus that first crossed over to humans in 1997 in Hong Kong. It has killed more than 150 people worldwide since then, most of them in Asia. Most, but not all, were infected by contact with animals. Scientists are worried that the virus may mutate to a strain that can easily jump from human to human, and cause a global pandemic that could kill millions of people.

China's earlier reluctance to hand over the virus samples triggered speculation by some Western researchers. They alleged the Chinese were hoping to get a commercial advantage by being the first to come up with a new vaccine. China denied the allegations.