China, accused by the World Health Organisation of underreporting Severe Acute Respiratory Syndrome cases in Beijing, on Thursday refused to revise its toll.

But there was more evidence not all cases in China were being reported to the WHO.

The government declared one infection in the remote western region of Ningxia, but a doctor there said there were eight.

Hong Kong, the second most affected area after mainland China, said the virus had killed four more people and infected 29 others, while Australia reported its first three probable cases and India confirmed its first.

Southeast Asian leaders will meet in Bangkok on April 29 to hammer out ways of tackling the virus, which has struck a serious below to their economies.

"The Chinese government still has all along handled relevant problems with a scientific attitude, a responsible attitude, including understanding the outbreak, evaluating the outbreak and reporting," foreign ministry spokesman Liu Jianchao said.

An official at the Centre for Disease Control and Prevention, in charge of compiling data on SARS, also said the capital's toll had not changed.

"Up to this point, everyone knows, there are 37 clearly diagnosed cases," said CDC deputy general-director He Xiong. "I think government departments will definitely announce updates of such news to society as cases are diagnosed."

The WHO said on Wednesday Beijing might have five times the official tally.

WHO Executive Director for Communicable Diseases David Heymann said the WHO team of experts that visited two military hospitals estimated there were at least 50 SARS patients in one.

They 'estimated there are between 100-200 probable cases in Beijing, more than has been reported, and they feel that there might even be up to 1,000 people who are under observation right now', Heymann said in Geneva.

The illness has already spread to several provinces, cities and regions in the world's most populous nation and there are fears the disease may spread further when 100 million Chinese travel during a weeklong holiday in early May.

SARS has killed at least 65 people and infected 1,445 in mainland China -- nearly half of the world's cases.

The virus that causes SARS has been carried by travellers to around 23 countries, infecting more than 3,400 people and killing about 160 worldwide.

The first place it appeared outside Guangdong was in neighbouring Hong Kong, which has nearly as many cases and, as of Thursday, the same death toll as mainland China.

Sixty-five of the 1,268 people who have caught the disease in the former British colony have died, including some in a high-rise complex where more than 300 came down with it.

Singapore and Hong Kong, both hit hard by the virus, are checking airline passengers for fever.

The WHO confirmed that a member of the coronavirus family never before seen in humans caused SARS, which is contagious, sometimes fatal and has no known cure.

Experts said they were optimistic the disease could be controlled using existing measures, but the coronavirus family tended to mutate relatively quickly.

Economists estimate the epidemic has already caused at least $30 billion in losses worldwide and will pose more of a threat to Asia's economic growth than the war on Iraq, through lower tourist earnings and reduced consumer spending.

(Additional reporting by Jason Szep in Singapore, Karen Iley in Geneva, John Ruwitch in Beijing and Tan Ee Lyn in Hong Kong)

The SARS Outbreak: The Complete Coverage