China has begun implementing draconian quarantine measures to try to curb the spread of the pneumonia-like Sars virus.
Correspondents report a growing mood of alarm in Beijing
Whole villages have been sealed off, along with a hospital in Beijing reported to have more than 100 infected patients.
Thousands of people are taking trains and planes out of Beijing, where another four deaths have been announced.
The move came a day after the World Health Organization (WHO) added Beijing, Toronto and China's Shanxi province to the list of places it is advising travellers to avoid.
The WHO has also sounded an alert about the situation in China's second city, Shanghai.
WHO expert, Dr Wolfgang Peiser, who is visiting the city, said he believed there were tens of Sars cases there, rather than the two officially confirmed cases.
KNOWN DEATH TOLL
Hong Kong: 109
Source: WHO/ local health authorities
Hong Kong has also announced four more deaths and 30 new cases of Severe Acute Respiratory Syndrome, taking the territory's death toll to 109.
Health officials in Hong Kong have been checking the temperature of hundreds of people crossing the border from mainland China.
World economists have meanwhile warned that the virus would have a major impact on growth rates in East Asia.
The Organisation for Economic Co-operation and Development said tourism and retail sectors were already suffering.
The World Bank said Sars and the aftermath of the war in Iraq were likely to knock almost one-sixth off economic growth in Asia this year.
More than 250 people worldwide have died from Sars - including 16 in Canada, the worst-hit area outside Asia.
Tough measures in Beijing
In Beijing, police have sealed off the 1,200-bed People's Hospital of Beijing University because of multiple Sars infections.
But there was confusion over the measure. A doctor inside the hospital told the BBC that staff and patients were not being allowed to enter or leave the building.
But the authorities said all patients and medical workers had been moved from the hospital and were being held under observation elsewhere.
The city's schools have been closed for the next two weeks, affecting more than 1.7m children.
The authorities have ordered the isolation of all
Sars patients, those suspected of being infected, and buildings where the virus has been found.
The state news agency said anyone violating the order would be
The BBC's Holly Williams says there is a sense of spreading alarm in Beijing, with panic buying of rice and salt. Many tourists and foreign workers are reported to be leaving the capital.
In other developments:
- Parliament in Singapore debates new legislation requiring people thought to be infected to remain in their homes - those who refuse could be electronically tagged, fined or imprisoned. It comes as the health ministry announces two more people have died
- Bulgaria's health ministry reports the country's first suspected case. A man with symptoms of Sars is in hospital in the capital Sofia after returning from Toronto
- Russian airline Aeroflot says it is disinfecting all planes arriving from China, Vietnam, India and Canada
- Airline industry group IATA calls on Asian governments to reduce airport landing fees to help airlines cope with the Sars crisis
- Police in Australia are given new powers to round up and quarantine suspected Sars victims
The Indian Government calls all state health ministers to Delhi to draw up an action plan on Sars
Canada is furious that the WHO has advised travellers to avoid Toronto for the next three weeks. It has written to the organisation to challenge the move.
"There is no evidence of casual transmission of the disease in Toronto," government health officer Dr Paul Gully said. "We challenge the WHO's assertion that Toronto is an unsafe place to visit."
Canadian officials say all the cases in the country can be linked to a single cluster of health workers.
The WHO is helping to organise an international meeting on Sars in the Canadian capital Ottawa next week.
Before its latest advisory, the WHO had already warned against travel to Hong Kong and to China's southern Guangdong province, where the virus is believed to have originated late last year.