Announcing tough new travel restrictions, Hong Kong leader Carrie Lam said the government was planning to curb the sale of alcohol at more than 8,000 bars and restaurants, an extraordinary move in a city that never sleeps.

An emotional Lam said many people took off their masks in bars and "even have intimate acts when they are tipsy", increasing the risk of cross-infection.

"So, we are going to suggest, as it requires legislative work, around 8,600 restaurants, bars and clubs with liquor licenses to temporarily suspend the sale of alcohol by amending the law," Lam, who was wearing a face mask, told a news conference.

"We are investigating any further measures we can do rather than a complete closure of restaurants as we know many Hong Kong residents do not cook at home and often dine out."

Alcohol will be available in supermarkets and convenience stores across the city.

The city government announced 39 new cases of coronavirus on Monday, 30 of which had a recent travel history, bringing its total to 357. Four people have died of the disease in Hong Kong.

The measures come two days after the government warned a spike in the number of people returning to the region infected with coronavirus could lead to a large community outbreak.

The ban on tourist arrivals would last for 14 days from Wednesday, with visitors from mainland China, Macau and Taiwan who had travelled elsewhere recently, also subject to the restriction.

Late on Sunday, Hong Kong said it was investigating 41 instances of people violating quarantine, including five people who could face prosecution. Two had removed or cut off electronic wristbands used to track people, the government said.

Hong Kong last week began using the electronic wristbands linked to an app as part of its effort to enforce quarantine.