Cut off from worried families and sleeping in their offices, hundreds of medical workers are isolated with their patients as Beijing closes off entire hospitals amid sweeping measures to stop the spread of the Sars virus.

BEIJING city officials told 4,000 people suspected of being exposed to SARS to stay home yesterday, as quarantined medical workers in Taiwan held a rowdy protest and Hong Kong hospitals were accused of failing to protect frontline doctors from the deadly bug.

Struggling to contain Sars, Beijing officials sealed off a third hospital today, closed college dormitories and ordered 4,000 people who might have been exposed to the killer virus to stay at home under quarantine.