HONG KONG (REUTERS, AFP, BLOOMBERG) - Hong Kong on Monday (July 27) announced further restrictions to curb a surge in coronavirus cases, including a ban on gatherings of more than two people, a total ban on restaurant dining and mandatory face masks in all public places, including outdoors.

The measures, which will take effect from Wednesday, are the first time the city has completely banned dining in restaurants.

Hong Kong reported 145 cases of coronavirus on Monday, of which 142 were locally transmitted. Since late January, more than 2,600 people have been infected, 20 of whom have died.

"The situation is very worrying," said Chief Secretary Matthew Cheung, adding that the current outbreak is the most severe the city has experienced. The measures will be in place for 7 days, he said.

China will help Hong Kong build an emergency field hospital as coronavirus cases rise in the semi-autonomous city. "The central government has agreed to help us build a 'Fangcang Hospital'... which can provide up to 2,000 beds," Cheung told reporters, referring to the temporary facilities built in the Chinese city of Wuhan where the coronavirus first surfaced.

Hong Kong in July halted dine-in services from 6pm as concerns grew of a third wave of infections but allowed restaurants and cafes to function through the day as normal.

The city reported 103 local cases on Sunday, its fifth straight day of logging more than 100 cases.

About a third of the infections were of unknown origin, signalling that hidden chains of transmission were seeded in the community. Before this month, the reported number of daily locally transmitted infections had never topped 28.

Authorities had previously banned dining-in after 6pm and expanded mask-wearing requirements, from public transportation to indoor public venues.

However, the city has seen a spike in locally transmitted coronavirus cases over the past three weeks, with Sunday the fifth consecutive day of triple digit infection figures.

They have warned that citizens have become too lax about wearing masks and social distancing.

Over the weekend they stepped up controls, sealing off popular beaches and introduced new rules to limit movements of ship and flight crews which stop in the city.

The Asian financial centre has been taken off guard by the sudden jump of infections after managing to contain the spread locally as it tore across the world.

Its medical infrastructure is coming under strain - isolation beds and wards in public hospitals have reached 80 per cent capacity, and Hong Kong's total testing capacity is smaller than other places in the region that are also facing resurgences.

Unlike in some countries where it's mostly young people who are recently becoming infected, Hong Kong's current surge is affecting an older group of people, raising the likelihood of more cases turning critical.

China's liaison office in Hong Kong said on Sunday that the central government had made clear it would boost the city's capacity in coronavirus tests and help set up hospitals especially for infected patients.