China sealed off millions more people near the epicentre of a virus outbreak on Friday, shutting down public transport in an eighth city in an unprecedented quarantine effort as the death toll from the disease climbed to 25.

While the World Heath Organization held off on declaring a global emergency, despite confirmed cases in half a dozen other counties, China expanded a lockdown now covering some 26 million people and cancelled some Lunar New Year celebrations to prevent the disease spreading further.

The virus that emerged in the central city of Wuhan took eight more lives, the government said in its latest update, as the number of confirmed cases also leapt to 830.

The new virus has caused alarm because of its similarity to SARS (Severe Acute Respiratory Syndrome), which killed hundreds of people across mainland China and Hong Kong in 2002-2003.

The WHO said China was in a state of emergency, but it stopped short of making a declaration that would have prompted greater international cooperation, including possible trade and travel restrictions.

But Chinese authorities were taking no chances against a virus that has spread nationwide and to several other countries.

The normally bustling metropolis of Wuhan, a major industrial and transport hub in the centre of the country, slid deeper into surreal isolation as China tightened a transport cordon around it and nearby cities.

With hundreds millions of people travelling across the country this week for the Lunar New Year holiday, the government has halted all travel out of the city, municipal public transport has been suspended, and residents have been ordered not to leave home.

Very few flights were coming into Wuhan, too, further isolating the city from the rest of the world.

The measures have rendered the city of 11 million an eery ghost town, with streets and shopping centres deserted, and stores shuttered at a time normally marked by festive gatherings and shoppers out enjoying China's most important festival.

The city's police presence, usually quite prominent in China, was hardly detectable.

At a Wuhan hospital, AFP journalists saw medical staff in long rubber boots, masks and goggles, while apparently abandoned items were seen in the parking lot, including a pair of shoes, a pile of clothes and a wheelchair.

The scene was otherwise quiet with little sign of unusual activity.

"This year we have a very scary Chinese New Year. People are not going outside because of the virus," a taxi driver in the city, who asked not to be named, told AFP.

But he was not concerned about potential food shortages in a prolonged shutdown.

"No, because it's Chinese New Year and people have already bought a lot of things to cook at home for several days."

But the pathogen, known by its technical name 2019 Novel Coronavirus (2019-nCoV), has caused alarm throughout the country, with surgical masks selling out at pharmacies and stores in Shanghai, Beijing and other cities.

Besides Wuhan, seven other smaller cities nearby have taken measures to batten down the hatches.

In the latest, the city of Huangshi, which has a population of more than two million, announced Friday it had halted public transport and closed a major bridge.

On Thursday, Huanggang, a city of 7.5 million people, announced that public transport and train services were suspended and citizens were told to not leave the city.

The straitjacket on Wuhan tightened further Friday, with the city limiting the number of taxis allowed on roads from noon (0400 GMT), and hugely popular Chinese ride-hailing service Didi Chuxing saying it was temporarily suspending services there.

To discourage nationwide holiday travel, the government said beginning Friday anyone who bought a ticket for rail, air, long-distance coach, or water transport could receive a refund upon cancellation.

Beijing has cancelled massive gatherings that usually attract throngs at temples during the New Year holiday, while the historic Forbidden City will close from Saturday.

The respiratory virus emerged from a seafood and animal market in Wuhan in late December. It has spread to several other countries including the United States.

The National Health Commission said that of the 830 cases in China so far, 177 are in serious condition. Authorities were also examining 1,072 suspected cases.

"This is an emergency in China, but it has not yet become a global health emergency," WHO chief Tedros Adhanom Ghebreyesus told reporters after two days of talks in Geneva.

Tedros hailed China for taking the preventive measures but added "we hope that they will be both effective and short in their duration."

China has been praised for its response, in contrast to the SARS epidemic when it took months to report the disease and initially denied WHO experts any access.

China confirmed Thursday the first virus death outside the Wuhan epicentre, an 80-year-old man in Hebei province, near Beijing.

Health authorities have said most fatalities have been aged between 48 and 89 and already suffered from pre-existing health conditions.

Copyright AFP. All rights reserved.

China seals off more cities
The Huanan Seafood Wholesale market in Wuhan is thought to have been the source of the deadly pathogen. Photo: AFP / Hector RETAMAL