BEIJING (AP) - China ordered all public schools in its capital closed Wednesday, leaving almost 2 million students to study at home following a major jump in the number of reported SARS cases in the city.

The closure begins Thursday and lasts for two weeks through what would have been the May Day school holiday, said an official of the Beijing Municipal Education Commission. The official, who would give her name only as Miss Cui, said tests for primary, junior high and high school students were postponed indefinitely.

Cui wouldn't give a reason, but Beijing newspapers cited a government notice that said it was meant to prevent the spread of severe acute respiratory syndrome, which has killed at least 28 people in the Chinese capital. The closure will effect about 1.7 million students.

On Tuesday, Hong Kong reopened most secondary schools three weeks after they were closed to help contain the ailment.

China's health ministry said on Sunday Beijing's number of infections had surged nearly tenfold from 37 to 339. More triple-digit increases were announced Tuesday and Wednesday, raising Beijing's total cases to 588.

The Beijing Morning News said students with Internet access would receive lessons at home, and teachers would be required to come to work to supervise their studies.

Chinese authorities on Sunday called off the weeklong May Day vacation period in hopes of preventing tens of millions of Chinese from traveling and possibly spreading the virus. They later restored five days, but travel agencies were barred from transporting tour groups from one province to another.

Nationwide, China has reported 106 deaths from SARS and says it has more than 2,100 people infected. Six new SARS deaths were reported in Hong Kong on Wednesday, pushing the territory's toll to 105.

An estimated 4,000 people worldwide have been infected by SARS, and about 250 have died, mostly in Asia. The United States has reported just 38 probable cases and no deaths.

Most of mainland China's deaths and infections are in Guangdong, the southern province where the disease is suspected to have originated. But new cases are being reported daily in areas ranging from central China to its northwestern desert regions and northern grasslands.

Beijing's mayor was replaced Tuesday after the city government was accused of mishandling the outbreak. The World Health Organization said city officials failed to trace patients who might have been exposed, which the U.N. agency said could let the disease spread.

Elsewhere, the eastern city of Hangzhou has called off community programs in school facilities and closed school playgrounds and sports fields to outsiders, newspapers reported.

They said schools throughout the country have been ordered to step up work on disinfecting their facilities and teaching students hygiene, but no other closures were immediately reported.

In Beijing, an infrared body temperature scanner has been set up at the capital's airport to check passengers for fever, a SARS symptom, news reports said. They said similar devices are to be set up at train stations and airports in Shanghai, the county's biggest city.

In Hong Kong, the World Health Organization said it had doubts about a government report blaming sewage leaks and personal contact for a huge outbreak at an apartment complex. More than 300 people caught the disease at the Amoy Gardens apartments, and 14 have died.

Studies by Hong Kong researchers showed the SARS virus can survive for at least 24 hours on a surface coughed on or touched by a victim, longer than the three hours some had previously thought.

''The virus is very obstinate. It is very difficult to kill,'' microbiologist John Tam of the Chinese University of Hong Kong said in a radio interview broadcast Wednesday.

The Mormon Church said Wednesday it has temporarily stopped sending missionaries to Hong Kong as a precaution against SARS, and those already on the streets here are wearing masks and avoiding contact such as handshakes. None of Hong Kong's 30,000 Mormons are known to have caught SARS.

Hoping to ease the economic strains from SARS, Hong Kong officials said they will temporarily cut taxes, lower some charges and guarantee bank loans as part of a $1.5 billion assistance package.

In Canada, the SARS death toll rose by one on Tuesday, to a total of 15.

Australia's most populous state, New South Wales, said it will allow authorities to quarantine suspected SARS sufferers. Australia has had just three probable cases of SARS, all members of one family who have recovered.

Hawaii, which receives many visitors from Asia, so far seems safer than many locales, the incoming director of the WHO said Tuesday. There are only five suspected cases of SARS in Hawaii, two of which are designated ''probable'' infections.