The World Health Organization has issued a travel warning for parts of China and Toronto, Canada in order to halt the spread of the deadly Severe Acute Respiratory Syndrome virus.

The World Health Organization is recommending that people postpone non-essential travel to China's capital, Beijing and Shanxi Province.

It also warns against travel to Canada's business capital Toronto, in order to halt the spread of the deadly SARS virus. It says that the outbreak in Toronto has continued to grow in magnitude, and has affected people beyond the initial risk groups of hospital workers, families of the first victims, and other close person-to-person contacts.

The health agency says the travel advice will be re-examined in three weeks, which is twice the maximum incubation period for SARS .

According to the agency's latest tally, about 4,000 people have the disease worldwide, and 217 are reported to have died from SARS, with new deaths and new suspected or confirmed cases being announced daily. SARS has defied health checks at airports and borders to spread to more than 25 countries since late February.