Hong Kong reported 37,529 new coronavirus infections on Saturday and 150 deaths, as the city clings to a "zero-Covid" strategy despite spiralling cases that have spread through care homes and overwhelmed healthcare facilities.

Many supermarket shelves were bare again on Saturday even as the government said there was plenty of fresh food supplies from the mainland and the public should not over-purchase.

Two of the city's largest consumer retail chains started rationing some food and drug items on Friday to curb panic buying amid fears of a citywide lockdown.

Hong Kong leader Carrie Lam has said there will not be a "complete lockdown" although many residents are unnerved and frustrated by what they see as mixed messages and policy tweaks on an almost daily basis.

Health authorities said on Saturday more than 900 care homes have been infected. The latest tally of 37,529 cases is down from 52,523 on Friday. This compares with about 100 infections at the start of February and a clean three-month streak of zero cases before the end of December.

As cases hit record highs, Hong Kong now has its most stringent restrictions in place since the pandemic started, with group gatherings limited to two people, masks compulsory and gyms, cinemas and most public venues closed. Flights into the city from nine countries are banned.

Government expert adviser Professor David Hui said on Saturday he believes around 15% of Hong Kong's 7.4 million people are already infected with Covid-19, broadcaster RTHK reported.

The jump in Covid-19 infections has limited manpower in the health care system, and for public transport, mall operators, supermarkets and pharmacies.

On Saturday, Hongkong Post said it would stop providing local courier and parcel services from Monday until further notice, focusing instead on "essential services" as infections rise.

Hong Kong has reported more than 403,000 cases of Covid since the coronavirus emerged in late 2019 and at least 1,560 deaths, far fewer than many other cities. Most infections and deaths were recorded in the past month.

While Hong Kong clings to its "zero-Covid" policy, frustrations in the city are boiling over, workplace morale is being hit hard and families are splitting as a growing number of people, especially expatriates, abandon the global financial hub.