Hong Kong's total number of coronavirus cases reached 100 on Monday after the city reported two more confirmed infections, involving a man who had been in close contact with a virus-stricken patient and a woman who had returned from the Diamond Princess cruise ship.

The 99th case is a 68-year-old woman with underlying illnesses who was among the suspected patients on Sunday.

She returned to Hong Kong on a government-chartered flight on Feb 22 from the cruise ship docked in Japan, and developed a fever and a cough. She is in stable condition.

The 100th case involves a 63-year-old man with an underlying illness, who is the older brother of a 60-year-old female patient confirmed to have the virus on Feb 25.

He was asymptomatic and had earlier been sent to a quarantine center as a close contact of an infected patient. He had no travel history during the incubation period of the virus.

A 56-year-old man with a record of good health tested initially positive for the pathogen, and is awaiting a final diagnosis. He had also returned from the Diamond Princess, which saw over 700 people on board infected with the virus.

The SAR's health authorities urged the public to always keep a safe distance from other people when socializing, as Hong Kong is experiencing a "small-scale community outbreak" of the coronavirus.

At a press briefing on Monday, Chuang Shuk-kwan, head of the communicable disease branch of the Centre for Health Protection of the Department of Health, advised members of the public to avoid social activities to minimize the risk of contracting the disease in small gatherings.

She noted that many confirmed patients in the city had contracted the disease from people they came into contact with, including a cluster of 16 infections linked to a Buddhist worship hall at a residential building in North Point. Another 13 infections were linked to a family hotpot gathering during the Lunar New Year holiday.

In another development, the Macao government on Monday has resumed operation and the city's casinos have fully reopened for business.

Long lines of people were seen at government buildings. Anyone entering government buildings has to have their body temperature checked and produce a valid health certificate.

Entertainment venues, including casinos, bars and clubs, have to comply with quarantine guidelines. This includes all employees having to wear face masks; people with respiratory symptoms will be banned from entering.

As of Monday, eight of Macao's 10 patients had been discharged from hospitals.