Chinese scientists have started clinical trials of the world's first vaccine against the deadly disease SARS on four young volunteers in Beijing, the state media reported on Monday.

The volunteers were in good conditions on the first day of the world's first clinical testing of a vaccine for Severe Acute Respiratory Syndrome (SARS), China Daily said.

The four volunteers, including three healthy male students and a female from Beijing-based universities, were injected a SARS vaccine or a SARS-virus free placebo on Saturday afternoon, an official in charge of the experiment said.

During two hours of observation period after the inoculation, no abnormal reaction was observed and they left China-Japan Friendship Hospital in Beijing where the testing was conducted.

The volunteers would take blood tests and be observed for reaction everyday in the first three days, and the whole observation process would last 210 days.

Neither the volunteers nor the doctors were informed of whether the injection is a vaccine or a SARS-virus free placebo, the report said.

The four are the first group of 36 healthy volunteers selected for the testing. They will be inoculated either with the vaccine or a placebo.

Doctors of the hospital said they are well prepared to deal with any emergencies that might happen to the volunteers.

Approving the first phase of the clinical testing in January this year, China has become the first nation in the world to approve clinical testing of the vaccine on humans.

The vaccine was developed by Beijing Kexing Bio-Product Company Limited.