Hong Kong's government is widening its quarantine to include people exposed to suspected, as well as confirmed, SARS sufferers as doctors struggle to identify those infected with the deadly virus.
The city also extended a closure of primary schools and announced plans to step up border checks, as the Severe Acute Respiratory Syndrome (SARS) death toll in the city rose by four to 109.
Some recently diagnosed patients did not display typical SARS symptoms, raising concern about the ability of authorities to quickly identify others exposed to the virus.
SARS symptoms include high fever, a dry cough, muscle aches and breathing difficulties. Some patients also have diarrhoea.
Hong Kong has banned 787 close contacts of confirmed SARS patients from leaving home for 10 days. The Hong Kong government announced 30 more infections, taking the total to 1,488 in the worst-hit centre outside mainland China.
In China, a major Beijing hospital has been sealed off in a bid to contain the virus threatening to erupt across the nation. Hours after the World Health Organisation advised people against visiting the city, police took positions around the 1,200-bed Beijing University People's Hospital in the middle of the night to stop people going in or out.
It was the latest dramatic action by a government that declared war on SARS last week, five months after the virus first appeared in the southern Chinese province of Guangdong and started spreading around the world.
Mainland China has reported 106 of the 254 killed by SARS so far and more than half of the 4,500 infections worldwide.
Singapore reported another death overnight to take its total to 15 known deaths and two suspected ones. The city-state said all visitors entering and leaving will have their temperature checked at the airport or at land crossings.
There was outrage in Canada as the WHO added Toronto - in addition to Beijing, Hong Kong, Guangdong and Shanxi provinces - to a list of places to avoid because of SARS.
Canada has 330 cases of SARS and 16 deaths, most of them in Toronto, which has a large Chinese population.