Hong Kong's Disneyland announced it was shutting its doors on Sunday until further notice over the deadly virus outbreak in central China, a day after city authorities classified the crisis as an emergency.

The park said it was taking the step to protect "the health and safety of our guests and cast members", mirroring a similar move by Shanghai's Disneyland.

Ocean Park, a rival amusement park on Hong Kong's main island, said it was also closing its doors.

On Saturday, Hong Kong classified the outbreak as an "emergency" -- the city's highest warning tier -- and announced ramped-up measures to reduce the risk of further infections.

The move came as city leader Carrie Lam faced criticism in some quarters over her administration's response to the crisis.

Calls have been made by politicians and some medical experts to halt, or limit, arrivals from the Chinese mainland where the epidemic began.

Of the six people to have tested positive for the virus, five arrived via a newly built high-speed train terminal which connects with the mainland.

On Sunday, a newly formed union which represents healthcare workers threatened industrial action from February 3 if the government does not ban all arrivals from mainland China.

And in the district of Fanling, local residents held a protest against plans to earmark an empty public housing block as a temporary quarantine for patients and frontline medical staff who don't want to return to their families.

Lam has resisted closing the border, saying the crisis is not yet at a point where such a drastic measure is needed.

But she has announced all mainland arrivals must now sign health declaration forms.

A series of public events, including a Lunar New Year gala and next month's marathon have also been cancelled while the re-opening of schools after the holidays has been delayed.

On Sunday, the nearby gambling hub of Macau announced three more cases of the novel coronavirus, bringing its total to five.

All three new cases were women who came from the central Chinese city of Wuhan, the epicentre of the outbreak. One of the women had arrived in Macau via Hong Kong, authorities said.

The closure of Disneyland and Ocean Park will pile fresh misery on Hong Kong's tourism, leisure and retail sectors which have already been battered by more than seven months of often-violent pro-democracy protests.

Ocean Park is on track to receive a HK dollar 10.6 billion (USD 1.3 billion) government bailout over grim ticket sales in recent years.

Combined with the US-China trade war fallout, the protests have helped tip Hong Kong into recession and the virus outbreak has only compounded the city's economic woes. Lam's approval ratings are languishing at record lows after the protests but Beijing has doggedly stuck by her.

Hong Kong has firsthand experience of deadly viral outbreaks.

Nearly 300 people were killed in the city by Severe Acute Respiratory Syndrome (SARS) in 2003, a tragedy that left a profound psychological impact on one of the most densely populated places on earth.