Hong Kong will impose strict new social distancing measures from midnight Tuesday, the most stringent in the Asian financial hub since the coronavirus broke out, as authorities warn the risk of a large-scale outbreak is extremely high.

The measures dictate that face masks will be mandatory for people using public transport and restaurants will no longer provide dine in services and only offer takeaway after 6 pm.

Both are new rules that were not implemented during the city’s first and second coronavirus waves earlier this year. If a person does not wear a mask on public transport, they face a fine of HK$5,000 ($645).

Earlier on Monday, Chief Executive Carrie Lam said that the government would limit group gatherings to four people from 50 – a measure last seen during a second wave in March.

“The recent emergence of local cases of unknown infection source indicates the existence of sustained silent transmission in the community,” the government said in a statement late on Monday.

Earlier, Health experts suggested that the city could be considered to be free of local transmission if there were no such cases after 28 days, or two incubation cycles for the coronavirus.

Hong Kong residents were able to go to gyms, beauty parlours, bars, restaurants, and other public venues which were closed for more than a month after city officials allowed a partial reopening of eight types of businesses, but with conditions.

Lam said the measures were the result of a three-way tug of war between considerations related to public health, economic impact and social acceptability and that the city may need to co-exist with the virus for a period of time.

In May, Lam announced the relaxation of social distancing measures, including allowing some entertainment venues to reopen and schools to resume classes, as the COVID-19 pandemic was, what she claimed, subsiding in the city.

Meanwhie, the overall number of global COVID-19 cases has surpassed the 13 million mark, while the deaths have increased to more than 572,000, according to the Johns Hopkins University.

Infections have been reported in more than 210 countries and territories since the first cases