China shut part of the Great Wall and suspended public transport in 10 cities, stranding millions of people at the start of the Lunar New Year holiday on Friday as authorities rush to contain a virus that has killed 26 people and infected more than 800.

The World Health Organisation (WHO) has declared the new corona virus an “emergency in China” but stopped short of declaring it of international concern.

While restrictions on travel and gatherings have already been imposed to curb the outbreak, China will take stricter and more targeted measures, state television reported citing a State Council meeting on Friday, but gave no further details.

“The spread of the virus has not been cut off ... Local authorities should take more responsibility and have a stronger sense of urgency,” state broadcaster CCTV said.

The defence ministry said it is organising military medical experts to take part in the fight against the virus, without giving details.

Most of the cases and all of the deaths have been in China, but the virus has also been detected in Thailand, Vietnam, Singapore, Japan, South Korea, Taiwan, Nepal and the US.

Britain convened an emergency response meeting on Friday.

While health officials have been at pains to say it is too soon to evaluate the severity of the outbreak, the newly identified coronavirus has triggered alarm because it is too early to know how dangerous it is and how easily it spreads.

Symptoms include fever, difficulty breathing and coughing. Most of the fatalities have been elderly, many with pre-existing conditions, the WHO said.

As of Thursday, there were 830 confirmed cases and 26 people had died there, China’s National Health Commission said.

Most cases have been in Wuhan, where the virus is believed to have originated in a market that traded illegally in wildlife. Preliminary research suggested it crossed to humans from snakes.

China has advised people to avoid crowds and 10 cities in the central province of Hubei, where Wuhan is located, have suspended some transport, the Hubei Daily reported.

The week-long celebrations to welcome the Year of the Rat began on Friday, raising fears the infection rate could accelerate as hundreds of millions of people have already travelled to see family at home and abroad. The city of 11 million people, and neighbouring Huanggang, a city of 7 million, were in virtual lockdown. Nearly all flights at Wuhan’s airport had been cancelled.

Checkpoints blocked the main roads leading out of town, and police checked incoming vehicles for wild animals. About 10 people got off a high-speed train that pulled into Wuhan on Friday afternoon but nobody got on before it resumed its journey. Although it stopped there, Wuhan had been removed from the train's schedule.

“What choice do I have? It’s Chinese New Year. We have to see our family,” said a man getting off the train who gave his family name Hu.

Some sections of the Great Wall near Beijing will be closed from Saturday, state media said.

Some temples have also closed, including Beijing’s Lama Temple where people make offerings for the new year, have also been closed as has the Forbidden City, the capital’s most famous tourist attraction.

Shanghai Disneyland will close from Saturday. The theme park has a 100,000 daily capacity and sold out during last year's new year holiday. Film premieres have also been postponed and McDonald’s suspended business in five cities in Hubei province.

In Wuhan, where the outbreak began last month, pharmacies were running out of supplies and hospitals were flooded with nervous resident seeking medical checks.

The city was rushing to build a 1,000-bed hospital for the infected by Monday, the official Changjiang Daily reported.