Three more Asian countries confirmed coronavirus infections yesterday among citizens who had not travelled to China, as Hong Kong reported its first death from the disease and millions more people in Chinese cities were ordered to stay indoors.

The toll in mainland China soared to 425 after 64 more people died, the biggest single day tally since the first fatalities emerged last month. 2 more people died of the virus outside China.

More than 20 countries have confirmed cases of the virus, prompting the World Health Organization to declare a global health emergency, several governments to institute travel restrictions, and airlines to suspend flights to and from China.

But it has continued to spread with Singapore, Malaysia, and Thailand yesterday reporting new infections that were not imported from China.

In a sign of growing concern about a spread to other densely-populated Chinese metropolitan areas, authorities in three cities in eastern Zhejiang province -- including one near Shanghai -- limited the number of people allowed to leave their homes.

Three districts in Hangzhou -- including the area where the main office of Chinese tech giant Alibaba is based -- now allow only one person per household to go outside every two days to buy necessities, affecting some three million people.

The city is only 175 kilometres (110 miles) southwest of the financial hub of Shanghai, which has reported more than 200 cases, including one death, so far.

Similar measures were imposed in Taizhou and three districts in Ningbo, covering a total population of nine million people.

Days before, similar restrictions were placed on Wenzhou, home to another nine million.

Zhejiang province has confirmed 829 cases -- the highest number outside the central region of Hubei, whose capital, Wuhan, is the epicentre of the outbreak.

The disease is believed to have emerged in December in a Wuhan market that sold wild animals, and spread rapidly as people travelled for the Lunar New Year holiday in late January.

China has struggled to contain the virus despite enacting unprecedented measures, including virtually locking down more than 50 million people in Hubei.

On Sunday the Philippines reported the first death abroad: a Chinese man who had come from Wuhan.

All British nationals were advised yesterday to leave China “if they can” to minimise their risk of exposure to the deadly novel coronavirus.

The death of the 39-year-old man in Hong Kong came as the semi-autonomous city closed all but two land crossings with the Chinese mainland. Hong Kong media said the man had underlying health issues that complicated his treatment. He had visited Wuhan last month and his 72-year-old mother was also infected.

With more than 20,400 confirmed infections in China, health officials yesterday noted that the mortality rate for the new coronavirus stood at 2.1 percent, with most victims either old or with underlying health problems. SARS killed nearly 10 percent of patients.

There have been nearly 200 cases elsewhere across 24 countries and China’s special administrative regions Hong Kong and Macau.

Singapore announced Tuesday its first four cases of people being infected locally, bring the total number of infections to 24.

Macau, China’s semi-autonomous gambling hub that is popular with mainland Chinese visitors, decided to temporarily close all of its casinos for at least two weeks.