Chinese authorities ordered doctors in Beijing to hide SARS patients from a team of World Health Organization experts last week in an attempt to play down the extent of the epidemic, Chinese doctors and other sources said today.

Authorities transferred about 40 patients with severe acute respiratory syndrome to a hotel on the grounds of one hospital, and at another facility moved more than 30 SARS patients into ambulances to prevent the WHO team from finding them, the sources said.

A worker at the Zihuachun Hotel, on the grounds of People's Liberation Hospital No. 309, said several dozen patients were taken to the hotel Tuesday morning, the day WHO officials visited two military hospitals. The patients were moved back to the hospital that evening, he said.

Doctors at the Sino-Japanese Friendship Hospital said 30 SARS patients, all medical personnel, were packed into ambulances while a WHO team visited the hospital.

"It was done to avoid detection by the WHO. We drove the patients around Beijing," said a senior medical official at the hospital. "We were ordered by the Beijing government. We don't know if the central government was aware, but we assume it was."

The doctors, who spoke on condition of anonymity, confirmed a report published Friday on the Web site of Time magazine. The actions, which doctors said were ordered by the Beijing city government and the Chinese army, mark the most egregious in a series of steps taken by the Chinese government to cover up the extent of the epidemic.

A Western medical researcher said this type of behavior is common in China. While researching drug-resistant tuberculosis in another province, she said, she discovered patients being kept in an elevator because the hospital did not want her to have an accurate picture of the problem.

WHO officials have raised concerns that China was lying about the seriousness of the SARS epidemic and have said they believed that the government was getting the message. On Friday, President Hu Jintao and Premier Wen Jiabao called on officials to stop underreporting the number of SARS cases. Wen also warned that officials would be punished if they misreported the seriousness of the disease. Chinese sources said they expected officials to issue new statistics on the disease Sunday.

The official toll in Beijing, for example, is 37 people infected with SARS. But doctors say the real number is at least 200. Chinese doctors said the government would explain the big jump by saying they have adopted a new, less strict definition of SARS.

"The reality, however, is that we've been hiding patients," said a doctor at Youan Hospital, which is believed to have as many as 100 patients but has reported only 20.

In Beijing, authorities are beginning to take stringent measures to contain the disease. University students are now banned from leaving campus without a letter of permission from their teacher, students said. At least one student has already died at Beijing University of Foreign Economics and Trade, classmates said. In other cities, such as Taiyuan, in the poverty-stricken province of Shanxi, schools have been ordered closed until May 8, officials in the city said.

SARS is believed to have originated in China in November. Doctors in the province of Guangdong recognized it as a new and virulent disease by mid-December, doctors there said. But provincial officials did little to deal with the disease until early February, and officials in Beijing waited until late March. Other provinces are even further behind.

Hong Kong announced today that 12 more people had died in the territory, the highest one-day death toll reported. The WHO said SARS appeared to have become more severe in a particularly alarming and puzzling outbreak in an apartment building in the territory. The disease seemed to have struck younger, healthier people, raising the possibility that "the virus may have mutated into a more virulent form," the WHO said. The SARS virus belongs to a family of viruses that "are known to mutate frequently," the WHO said.

The health organization also said a recent outbreak of SARS among members of a religious group in Canada was "particularly disturbing because of its potential to move into the wider community." One member of the group may have spread the disease at two prayer meetings, on March 28 and March 29. Twenty-nine members of that group, as well as two doctors who treated them, have been infected. The WHO fears there may be "multiple additional exposures." Health authorities were tracking down everyone who had contact with affected members to "work to prevent further spread of cases."

Toronto has been fighting the worst outbreak of SARS outside of Asia. Canadian health officials reported today that a 99-year-old man has died from the disease, raising the death toll in Canada from the virus to 14. The news of the death came as officials reported a new "cluster" of cases at Toronto's Sunnybrook Hospital, closing the hospital's trauma and intensive care units, after four health care workers at the hospital began showing symptoms. Eight other staff members are under investigation.

In Vancouver, officials closed a ward at Royal Columbian Hospital after a report that a second nurse may have contracted SARS. Officials have placed 13 patients and 40 workers at the hospital in isolation.

SARS has infected more than 3,500 people and killed 182 in 25 countries, according to the WHO.

Staff writers Rob Stein in Washington and correspondent DeNeen L. Brown in Toronto contributed to this report.

President Hu Jintao, left, and Premier Wen Jiabao finally called on Chinese officials on Friday to stop underreporting the number of SARS cases.