Younger children are expected to go back to school next week

About 200,000 children from around 400 schools went back to class, although 10 schools refused to open.

Most children had their temperatures taken at home before leaving for school - a new requirement in the fight against severe acute respiratory syndrome.

Sars has infected 1,402 people in Hong Kong. There have been 94 deaths, although 436 people have recovered and been discharged from hospitals.

In China, where the outbreak is thought to have started, official newspapers on Tuesday urged people not to travel to the countryside.

The authorities are worried that China's poor rural health care system cannot track or cope with the virus, which has started spreading from richer coastal areas to poorer provinces inland.

BBC correspondent Holly Williams, in Beijing, says the Chinese Government could soon be producing 100,000 Sars test kits a day.

The kit, using a method called the Enzyme Link Immuno Adsorbent Assay (Elisa), could detect Sars within an hour, it is claimed.

Mainland China's official death toll from Sars stands at 92, with 2,001 cases.

Of those, 25 deaths and 482 cases were in Beijing.

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Although most secondary school children in Hong Kong are back at school, another 900,000 younger students are not expected to return to class until next Monday.

And there were even delays for those who did go back as some of them forgot to have their temperatures taken at home.

Students were seen lining up to have their temperatures taken, a job hampered because some schools were having trouble obtaining thermometers.

They could not get ear thermometers and had to rely on oral thermometers - which took longer to use and created more risks of personal contact and so infection, local radio reported.

Cover-up

In Beijing, shops, restaurants and hotels are empty and locals in Hong Kong say their city is a ghost town, according to our correspondent.

The pneumonia-like disease has now spread to four previously unaffected provinces in China, but most of the new cases are in Beijing.

The four provinces which now have Sars cases are the northern areas of Jilin and Liaoning, Zhejiang in the east, and Gansu in the north-west.

The Chinese Government has signalled a tough new approach to the disease, admitting a cover-up, sacking top officials and pledging more than $100m for disease control in its poorest provinces.

KNOWN DEATH TOLL Hong Kong: 94 China: 92 Canada: 14 Singapore: 14 Vietnam: 5 Thailand: 2 Malaysia: 1 Q&A: What is Sars? Are you affected?

There is no cure for Sars or vaccine for the virus. Health experts say the virus may never be fully eradicated.

Sars is believed to have originated in China's southern Guangdong province in November.

The World Health Organisation has identified the coronavirus - a virus family which causes the common cold - as the cause.

Sars has hit a number of countries around the world.

In Singapore, the authorities have placed 2,400 workers in quarantine and closed a large vegetable market for 10 days after a man working there was diagnosed with Sars.

Sars has also claimed 14 lives in Canada. The authorities closed the country's largest trauma unit for at least 10 days after four new cases of suspected Sars were discovered among health staff.