Hong Kong's leader defended her administration's use of "ambush lockdowns" on Tuesday after a spate of overnight operations to conduct surprise mandatory coronavirus tests uncovered no new cases.

The new tactic involves authorities giving no warning of an impending lockdown, sealing off buildings where cases are detected and then ensuring everyone inside is tested, usually overnight.

But the operations have had limited success.

Overnight on Monday police cordoned off designated areas in four densely populated districts. Authorities conducted some 1,700 tests but found zero new infections.

On Tuesday, city leader Carrie Lam said the ambush lockdowns were "not a waste of manpower and money but instead well worth" the resources.

"We can't take the number of confirmed cases as the sole or decisive standard," Lam told reporters. 

"Efficacy does not only concern recovery rate, but also prevention of the disease."

Hong Kong's government are taking a much more proactive approach to testing similar to tactics used on the authoritarian mainland as it struggles to contain a winter wave of infections.

On Tuesday morning, the government warned authorities would forcibly break into their apartments if law enforcement suspected people were hiding in their homes or refusing to submit a mandatory test.

Lam's de facto deputy  Matthew Cheung said officials would use "wider and more frequent" lockdowns as the city heads into the Lunar New Year holidays next week.

Hong Kong was one of the first places to be struck by the coronavirus after it spilled out of central China.

It has recorded nearly 10,500 infections with some 170 deaths by imposing effective but economically ruinous social distancing measures for much of the last year.