Moscow - The deadly pneumonia that has killed more than 100 people around the world may be a man-made biological weapon, Russian experts said on Friday.

Nikolai Filatov, head of Moscow's epidemiological services, told the Gazeta daily that he thought the pneumonia was man-made because "there is no vaccine for this virus, its make-up is unclear, it has not been very widespread and the population is not immune to it."

Yet he had some reservations, since the virus has a low mortality rate - so far killing 4% of those infected -, and because it is relatively difficult to pass on - through direct contact or inhalation.

The virus, according to academy of medecine member Sergei Kolesnikov, is a cocktail of mumps and measles, whose mix could never appear in nature.

"We can only get that in a laboratory," he told a conference in the Siberian city of Irkutsk, quoted by RIA Novosti news agency.

It may have spread because of an "accidental leak" from a lab, he added.

More than 100 people have died and some 3Ý000 others have been infected by Severe acute respiratory syndrome (Sars), which is believed to have originated in China's southern Guangdong province. Ý

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