China says a mysterious Sars-like virus has spread across the country, including to Beijing, raising concerns as millions begin trips for the Lunar New Year.
A day after state authorities said the virus was "controllable", officials said a third person was confirmed to have died and there were nearly 140 new cases.
The new coronavirus strain has caused alarm because of its connection to Severe Acute Respiratory Syndrome, which killed nearly 650 people across mainland China and Hong Kong in 2002-2003.
In Wuhan, the central city where the coronavirus was first discovered, 136 new cases were found over the weekend, the local health commission said, without giving details about the person who died.
Health authorities in Beijing's Daxing district said two people who had travelled to Wuhan were treated for pneumonia linked to the virus and are in stable condition.
In Guangdong, a 66-year-old Shenzhen man was quarantined on January 11 after contracting a fever and showing other symptoms following a trip to visit relatives in Wuhan, the provincial health commission said in a statement.
A total of 201 people have now been diagnosed with the virus in China. In Wuhan, 170 people are still being treated at hospital, including nine in critical condition, the city health commission said.
Wuhan is a city of 11 million inhabitants that serves as a major transport hub, including during the annual Lunar New Year holiday when hundreds of millions of Chinese people travel across the country to visit family.
In its first statement since the virus was detected, China's National Health Commission said on Sunday the disease's source was unknown but vowed to "step up monitoring" of any mutations during Chinese New Year period.
Chinese authorities said they had begun "optimised" testing of cases across the city to identify those infected, and said they would begin "detection work ... towards suspected cases in the city" as a next step, as well as carrying out "sampling tests".
Scientists from the MRC Centre for Global Infectious Disease Analysis at Imperial College in London have warned that the number of cases in Wuhan is likely to be closer to 1,700, much higher than the number officially identified. China is yet to confirm whether the virus can be spread from one person to another, but Wuhan's health commission has previously said the possibility "cannot be excluded".
China's centre for disease control sought to quash speculation about the coronavirus at the weekend, publishing a flyer that dismissed "five big rumours". One of them included claims about the coronavirus spreading, which China's disease control authority had dismissed at the time by saying all cases were being treated in Wuhan.
Although there has been no official announcement of screening measures on the mainland, Chen Xiexin, Wuhan deputy mayor, said infrared thermometers had been installed at airports, railway stations and coach stations across the city.
Mr Chen said passengers with fevers were being registered, given masks and taken to medical institutions. Nearly 300,000 body temperature tests had been carried out, according to state broadcasters.
Authorities in Hong Kong have also stepped up detection measures, including temperature checkpoints for travellers arriving from the Chinese mainland. The United States has said it will begin screening direct flights arriving from Wuhan at San Francisco airport and New York's JFK, as well as Los Angeles, where many flights connect.