HONG KONG - Authorities locked down parts of two streets in Kowloon on Tuesday night (Jan 26), hours after Hong Kong's leader warned that multiple small lockdowns could come, as pressure mounts on them to keep the pandemic under control.

Officials sealed off parts of Pitt Street and Tung On Street in Yau Ma Tei from 7pm, ordering people in the restricted area to be tested for the coronavirus. They aim to wrap up this blitz by 6am on Wednesday (Jan 27).

This came hours after Chief Executive Carrie Lam said future lockdowns in the city would be on a smaller-scale and more sudden than the one in Jordan over the weekend, even as the government expands compulsory testing in Kowloon and extends tough measures.

On Saturday (Jan 23), officials locked down an area in Jordan, also on the Kowloon peninsula, to get everyone there tested for Covid-19.

Part of the Yau Tsim Mong district, Jordan has recorded a higher number of cases than other parts of the city in recent weeks.

"Taking stock of our experience, we should be more focused in future testing operations, to narrow the scope of the area to, say, just a couple of streets or blocks. More of these smaller-scale operations can be done at different locations. This is something we will consider," Mrs Lam said at her weekly briefing ahead of the Executive Council meeting.

More than 7,000 people in 150 buildings were tested in the Jordan operation, with 13 cases detected.

Mrs Lam said more than 200 Jordan residents did not comply with orders to go for tests, urging them to do so. They could face fines of up to HK$25,000 (S$2,600) and a jail term of six months.

She said lessons learnt from the weekend operation in Jordan's restricted area include the need to seal off an area more quickly, being more "proactive and aggressive" in identifying carriers in the community, as well as cutting the time taken for communicating, testing and notification of test results.

Health authorities said at the daily briefing later in the day that Hong Kong would add more specified areas where mandatory testing orders would apply.

Dr Chui Tak Yi, Under Secretary for Food and Health, said the original specified area in Jordan would be expanded to include more developments and retain the existing Sham Shui Po one.

To further cut community transmission, the government will designate a specified area in Yau Ma Tei and Mong Kok, as well as one in Hung Hom.

"From today, in these four specified areas, any building with one or more unlinked confirmed cases, or where sewage samples tested positive showing risk of infection, will be subject to a compulsory testing notice.

"If a building has reported confirmed cases in the past 14 days, the government will prioritise sewage testing for these buildings and they'll be subjected to compulsory testing," Dr Chui said.

Rising case numbers in recent weeks from Yau Tsim Mong - a densely built district of old developments with cramped living conditions - had officials worried.

From Jan 1 to Jan 20, the specified Jordan area alone recorded 162 confirmed cases involving 56 buildings.

Some of the city's health experts have said the Jordan operation - a huge logistical undertaking that involved door-to-door roundups of residents for testing, 3,000 civil servants and 6,500 food packs - was not cost-effective. They said that existing measures including issuing mandatory testing notices, such as those in the Yau Tsim Mong and Sham Shui Po districts, have been effective.

Professor David Hui, a respiratory disease expert at the Chinese University of Hong Kong, had previously suggested that the fruit market near the lockdown in Jordan be sealed off as well, given the rise in cases in the vicinity. More than 70 cases were picked up from about 20 buildings near the fruit market.

But on Tuesday, he told a local radio station that this might not be necessary as authorities would order residents there to get tested.

Hong Kong recorded 64 confirmed cases on Tuesday, of which 63 were local and 21 untraceable. The number of total confirmed cases is now at 10,222 and 172 deaths.

In giving a breakdown of the "severe epidemic situation", Dr Chui said Hong Kong recorded 318 infections from Jan 12 to 18, of which 365 were local and 33 per cent untraceable.

From Jan 19 to 25, there were 494 cases where 469 were local and 41 per cent untraceable.

"In the past few weeks, asymptomatic cases made up 36 per cent of local infections," Dr Chui said, adding that current social distancing measures due to expire Thursday (Jan 28), such as capping public gatherings at two, and shutting gyms and bars, will be extended for another week to Feb 3.