The Chinese city at the center of the deadly new coronavirus became a war zone Thursday as authorities expanded their lockdown on the city to other areas to contain more than 30 million people.

The unprecedented quarantine came as officials revealed that the flu-like illness has killed 26 and infected more than 830 worldwide — and that it can spread far more easily between people than previously thought.

Public health authorities in Wuhan declared they were in a “state of war” as they locked down the central city of nearly 11 million people, where the outbreak was traced to a live-animal market in late December.

“Strictly implement emergency-response requirements, enter into a state of war and implement wartime measures to resolutely curb the spread of this epidemic,” a committee of Wuhan’s top officials urged.

“Homes must be segregated, neighbors must be watched.”

Hours after announcing the lockdown, authorities moved to cut off at least 10 nearby cities, placing under quarantine a total of more than 30 million people — more than the populations of New York City, Los Angeles and Chicago combined.

In Wuhan, soldiers and SWAT teams in face masks barricaded entrances to rail stations, as trains and planes out of the city were indefinitely suspended and subway and bus service halted.

People could still enter the city via car, but police were checking those in incoming vehicles for fever, coughing and trouble breathing.

Workers were disinfecting train stations and other public spaces.

“We are feeling as though it is the end of the world,” one Wuhan resident wrote on China’s Twitter-like Weibo platform.

Elsewhere across China, authorities moved to halt the virus.

Images from Fuzhou Changle International Airport showed passengers being removed in sealed quarantine boxes.

Beijing nixed plans for all large-scale Lunar New Year festivities, which were to run this year from Jan. 25 to Feb. 8.

Its most famous tourist attraction, the Forbidden City, was to close indefinitely Saturday.

Meanwhile, health officials revealed Thursday that the virus can spread more easily than previously thought.

“We are now seeing second- and third-generation spread,” said Dr. David Heymann, chair of the World Health Organization committee gathering data on the virus.

That means someone who caught the virus at the Wuhan market could spread it to a second person — who could then infect a third.

Initially, infection appeared to occur only with close contact, such as kissing or sharing eating utensils.

Now, Heymann told CNN, there’s evidence that more distant contact, like sneezing or coughing near a person’s face, can spread the virus.

The virus still is not believed to be transmittable across a room, like the flu or measles, he said.

Officials also reported the first death outside the outbreak’s epicenter.

In Hebei province — more than 600 miles north of Wuhan — an 80-year-old man died Wednesday after contracting the coronavirus strain, officials there said.

The other deaths had occurred in Hubei province, of which Wuhan is the largest city.

So far, many of the victims were over age 60 and had pre-existing health conditions, such as diabetes, hypertension or cirrhosis of the liver, China’s National Health Commission revealed Thursday.

In addition to the hundreds sickened in China, one case has turned up in the US and patients have been found in Japan, South Korea, Thailand and other Asian countries.

Still, the WHO said Thursday that it would not classify the outbreak as a global emergency.

“Make no mistake. This is an emergency in China, but it has not yet become a global health emergency,” said the UN agency’s director-general, Tedros Adhanom Ghebreyesus. “It may yet become one.”

A declaration of a global emergency provides more money and resources to affected areas, but could prompt foreign governments to cut off travel and trade to them.

Major international airports, including JFK and four other US hubs, have instituted screenings for travelers from China.

With wire services