A professor of geriatric medicine on Thursday questioned how long Beijing will be able to carry on with what she described as "draconian" measures to tackle Covid outbreaks.

Jean Woo from the Chinese University's Faculty of Medicine was speaking on RTHK's Hong Kong Today programme after the World Health Organisation called China's zero-Covid strategy 'unsustainable'. Foreign ministry spokesman, Zhao Lijian, labelled those remarks 'irresponsible'.

Woo said she saw insufficient evidence to show the effectiveness of locking down entire districts, as opposed to simply locking down a single block where an infection was found:

"If you detect a few cases, what is the area of isolation? What is the evidence to indicate what the area should be? I'm not aware of any studies to tell you that but it seems to be huge areas in lockdown, with consequences," Woo told RTHK's Samantha Butler.

"So I think shutting down transmission is important, but it's how you do it," she said.

Speaking on Tuesday, WHO chief Tedros Adhanom Ghebreyesus said China's zero-tolerance strategy was not sustainable and that it was time for a change in approach.

Addressing those comments at a press conference on Wednesday, Zhao said: "We hope the relevant individual can view Chinese Covid policy objectively and rationally and know the facts, instead of making irresponsible remarks." (RTHK/Reuters)