Shoppers thronged Hong Kong's markets fearing a shortage of food on Wednesday, familiar scenes in a city that is back under grueling COVID-19 restrictions in contrast to much of the world.

Hong Kong has followed mainland China in maintaining a strict "zero-COVID" policy that has kept infections low through targeted lockdowns and extensive social distancing measures.

On Tuesday the city recorded 625 new infections, a daily record but a number that pales in comparison with outbreaks around the world.

The omicron-fueled spike has alarmed authorities and leader Carrie Lam announced renewed curbs on the 7.5 million residents of the financial hub.

In scenes reminiscent of early 2020, when the coronavirus first emerged in China, Hong Kongers this week scrambled to stock up as panic set in over food supply shocks.

"It feels like the government isn't prepared at all, and we ordinary citizens can only look out for ourselves," a woman surnamed Siu, 42, told Agence France-Presse (AFP) Wednesday.

She was among the throng of morning shoppers anxious over fresh produce supply, which the city mostly imports from the mainland.

This week a cross-border truck driver tested positive for COVID-19, spurring a temporary hold-up of delivery trucks.

Hong Kong's vegetable supply has since decreased by about a third, the government said.

The shortage – coupled with business savvy among suddenly popular veg sellers – has sent produce prices in Hong Kong's wet markets soaring with shelves in supermarkets sitting bare.

"I don't remember vegetables ever being this expensive," Siu said, adding that her daily grocery bill had doubled this week.

Choy sum – a leafy green popular in Chinese cuisine – now costs around HK$25 ($3.20) for a half kilo, double its usual price.

A vegetable stall owner told AFP his supply, sparse earlier in the week, has recovered – for now.

"Hopefully things can get back to normal – I don't know how long we can keep this up," he said as he fielded shouted requests from customers.

'Very dispiriting'

Unlike much of the rest of the world – where governments opting to adapt to a new COVID-present normal have gradually opened up – Hong Kong's "zero COVID" policy has meant doubling down on restrictions.

Leader Lam on Tuesday said it was still the best strategy, given the city's low vaccination rate among the elderly, as she introduced new measures banning public gatherings of more than two people.

More significantly, Lam announced that meetings in homes of more than two families were forbidden.

She also ordered religious sites and hair salons to close by Thursday – sending Hong Kongers rushing to barbers for a last-minute trim.

Five hair salons in Central district said they were fully booked.

"They say the closure is temporary but who knows when it will reopen," a man surnamed Cheung told AFP as he waited for a haircut.

"It feels like we have gone back to the start of the pandemic. It's very dispiriting."

Hong Kongers also took to social media to express their frustration.

"We have done all you ask, we sat quietly as mental health takes a toll, as families are torn apart and as businesses close down because it is all in the hope of China reopening our borders," wrote one resident in an open letter that went viral.

"You have tried for two years, and failed," it continued.

"When will you stop holding the citizens of this... city hostage?"