Hong Kong will close most of the city's beaches, leader Carrie Lam said Wednesday, after photos of maskless residents enjoying sun and surf sparked outrage in mainland China.

The rules add to Hong Kong's already strict distancing measures, including wearing masks while hiking and a ban on gatherings of more than two.

"As we see a surge of people going to beaches, we have to take appropriate measures in order to protect our system, to reduce the public's movements to ensure safety," Lam told reporters.

Authorities said they will begin taping off the beaches Thursday.

Lam's announcement comes on the heels of anger from Chinese social media users, who have blamed the spread of Covid in the mainland on Hong Kong's sluggish epidemic response.

The city -- which recorded nearly 750,000 cases in less than three months -- has not gone into a full lockdown.

But tens of millions in mainland China were abruptly placed under stay at home orders this week, after the emergence of more than 3,000 daily new cases as Beijing battles to maintain its "dynamic zero" Covid strategy.

Nearby Shenzhen, with a population of 17 million, was locked down Monday after an Omicron flare-up in factories and neighbourhoods linked to Hong Kong.

"How can they be so carefree and go to the beach while Shenzhen is under lockdown? So selfish," one user wrote on Weibo.

"All of Guangdong province is crying for what Hong Kong has been doing," another wrote.

Researchers estimate the infection toll in Hong Kong is significantly higher than official figures, likely already reaching half its 7.4 million population.

The city's chief executive has taken hits from all sides on her handling of the crisis, with the spiralling deaths of a largely unvaccinated elderly population and unclear messaging about lockdown and mass testing.

Lam -- whose job is up for grabs in a few months -- has so far declined to say if she will run for another term.

The selection process was initially scheduled for March but was postponed to May because of the wave of Covid cases.

Any further postponement would be up to Beijing, Lam said.