President Xi Jinping said China was facing a "grave situation" as the death toll from the coronavirus outbreak jumped to 42, overshadowing Lunar New Year celebrations that began on Saturday.
China also announced further transport restrictions.
With more than 1,400 people infected worldwide, most of them in China, Hong Kong declared a virus emergency, scrapped celebrations and restricted links to mainland China.
Australia confirmed its first four cases and Canada its first on Saturday, after Malaysia confirmed four and France reported Europe's first cases on Friday, as health authorities around the world scrambled to prevent a pandemic.
The United States is arranging a charter flight on Sunday to bring its citizens and diplomats back from Wuhan, the central Chinese city at the epicenter of the outbreak, the Wall Street Journal reported.
In Hong Kong, with five confirmed cases, the city's leader Carrie Lam said flights and high speed rail trips between the city and Wuhan will be halted. Schools in Hong Kong that are currently on Lunar New Year holidays will remain closed until Feb. 17.
Xi held a politburo meeting on Saturday on measures to fight the "accelerating" outbreak, state television reported.
As of 8pm local time (1200 GMT) on Saturday, the death toll in China had risen to 42, authorities reported. Some 1,372 people in China have been infected with the virus - traced to a seafood market in Wuhan that was illegally selling wildlife.
The virus has also been detected in Thailand, Vietnam, Singapore, Japan, South Korea, Taiwan, Nepal, and the United States.
In Hubei province, where Wuhan is located, officials appealed for masks and protective suits.
"We are steadily pushing forward the disease control and prevention ... But right now we are facing an extremely severe public health crisis," Hu Yinghai, deputy director-general of the Civil Affairs Department, told a news briefing.
The newly identified coronavirus has created alarm because there are still many unknowns surrounding it, such as how dangerous it is and how easily it spreads between people. It can cause pneumonia, which has been deadly in some cases.
Ride-hailing giant Didi Chuxing said it was halting inter-city services to and from Beijing from Sunday, while the capital will also stop running inter-province shuttle buses.
State broadcaster CCTV, citing an announcement from China's tourism industry association, said the country would halt all group tours, both at home and abroad, from Monday.
Wuhan said it would ban non-essential vehicles from its downtown starting Sunday, further paralyzing a city of 11 million that has been on virtual lockdown since Thursday, with nearly all flights canceled and checkpoints blocking the main roads leading out of town.
Authorities have since imposed transport restrictions on nearly all of Hubei province, which has a population of 59 million.
Australia confirmed its first four cases in two different cities on Saturday, and the country's chief health official said he expected more cases as Australia is a popular destination for Chinese tourists.
Canada on Saturday identified its first case in a Toronto resident who recently returned from Wuhan.
State-run China Global Television Network reported on Saturday that a doctor who had been treating patients in Wuhan, 62-year-old Liang Wudong, had died from the virus.
US coffee chain Starbucks said it was closing all its Hubei outlets for the week-long Lunar New Year holiday, following a similar move by McDonald's in five Hubei cities.
Workers in white protective suits checked temperatures of passengers entering the subway at Beijing's central railway station on Saturday, while some train services in the eastern Yangtze River Delta region were suspended, the local railway operator said.
GLOBAL HEALTH THREAT'
There are fears transmission could accelerate as hundreds of millions of Chinese travel during the holiday, although many have canceled their plans.
Airports around the world have stepped up screening of passengers from China, although some health officials and experts have questioned the effectiveness of such screenings.
In an illustration of how such efforts could miss cases, doctors at a Paris hospital said two of the three Chinese nationals in France who have been diagnosed with the virus had arrived in the country without showing any symptoms.
The World Health Organization this week stopped short of calling the outbreak a global health emergency.
A report by infectious disease specialists at Imperial College, London on Saturday said that despite this, the epidemic "represents a clear and ongoing global health threat," adding: "It is uncertain at the current time whether it is possible to contain the continuing epidemic within China."
While China has called for transparency in managing the crisis, after a cover-up of the 2002/2003 Severe Acute Respiratory Syndrome (SARS) spread, officials in Wuhan have been criticized for their handling of the current outbreak.
In rare public dissent, a senior journalist at a Hubei newspaper run by the ruling Communist Party wrote on Friday on the Twitter-like Weibo social media platform that there should be an "immediate" change of leadership in Wuhan. The post was later removed.
Hubei province, where authorities are rushing to build a 1,000-bed hospital in six days, announced on Saturday that there were 658 patients affected by the virus in treatment, 57 of whom were critically ill.
Shanghai Disneyland was closed from Saturday. Beijing's Lama Temple, where people make offerings for the New Year, has also closed, as have some other temples.
Britain advised against all travel to Hubei and told its citizens in the province to leave.