“For those planning on going out or attending gatherings, can you reconsider and control yourself, so Hong Kong can win this fight?”

Since February, three people who came to Hong Kong from mainland China have been prosecuted for breaking quarantine orders.

Another five coming in from overseas have done the same, two of them leaving home to play basketball, and 36 have absconded from home quarantine.

Lam announced that starting from Tuesday midnight, non-residents would not be allowed into Hong Kong, transit passengers included, for a two-week period.

Anyone arriving from mainland China, Macau or Taiwan will be allowed in, she said, provided they had not travelled anywhere else in the past 14 days and subject to quarantine orders. Exemptions will be given to Macau residents previously registered with their own government.

Since last Thursday, when the city made it mandatory for all international arrivals to undergo quarantine, it has been allowing around 6,700 people in each day – about 90 per cent of them Hong Kong residents.

Lam had been under intense pressure to take similar action, with both pro-establishment politicians and opposition lawmakers urging her to get tougher.

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On Saturday she had questioned the need for a total ban on visitors, but on Monday she said the situation had changed to justify further action.

“We won’t sit on the situation … in fact, we’ve been thinking about and analysing [a ban] from Saturday,” Lam said, rejecting accusations she had been slow to act.

She also revealed that 1,100 returning Macau residents were due to transit Hong Kong in the coming days, but the city would continue to allow shuttle buses to carry them home from the airport.

Lam’s announcement caught the Macau government by surprise, according to its director of health, Dr Lei Chin-ion.

In an attempt to deter large gatherings of people in drinking and dining nightspots where clusters of infections have been reported, Lam said the government would amend the law to stop the sale of alcohol at 8,600 restaurants, bars and clubs holding liquor licences.

While she did not specify a time frame for the ban, only promising “swift” implementation, Lam confirmed it would be done through an amendment of the Prevention and Control of Disease Ordinance.

She also hinted the amendment, to be effective immediately upon announcement, would be general enough to allow further restrictions down the line.

“In restaurants, meals can still be served [without alcohol],” Lam said, explaining the rationale behind her move, “but in bars, people sometimes get intimate after drinking, and this will raise the risk of cross-infection.”

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Lam called on bar and restaurant operators to further restrict sizeable gatherings for events such as weddings, saying they would otherwise have to be made to comply using laws if they failed to act voluntarily.

The laws would provide flexibility to regulate the opening hours or capacity of restaurants, without even having to go through Lam’s cabinet for formal approval.

By Monday evening, 11 confirmed Covid-19 patients were known to have visited or worked in bars and restaurants in the city’s nightlife district Lan Kwai Fong, according to the Centre for Health Protection.

Lan Kwai Fong looked like a ghost town, and many pubs and bars across the city were mostly empty, although a few were still busy with customers.

The catering industry spoke out against the restrictions, saying they were excessive, while major associations in the business agreed to increase precautions against the coronavirus.

Lam said she was open to discussing with the sector how to support struggling operators.

“When all the restaurants and bars with a liquor licence are not allowed to sell and supply liquor, certainly their business will be affected,” she said.

“We certainly will consider what measures will be put in place to help these establishments.”

Lam also said the government could speed up prosecutions against those who flouted mandatory quarantine orders, with offenders facing a maximum HK$25,000 (US$3,205) fine and six months in jail if convicted. A hotline would also be set up to allow the public to report those suspected of violating home quarantine.

Lam said law enforcers had found five people who violated their home quarantine orders, and two who had cut their monitoring wristbands. They were sent to government quarantine camps and could face charges, she added. Police had also issued ­arrest warrants for 36 people who broke their home quarantine ­orders.

She pointed out that the city had fewer infections per capita on a global level.

“This war against the epidemic must carry on, this is a long fight,” she said.