A Chinese doctor reprimanded for warning of a "SARS-like" coronavirus before it was officially recognised died of the illness on Friday, triggering anger at the government.
The death of Li Wenliang, 34, came as President Xi Jinping reassured the United States and the World Health Organization (WHO) of transparency and maximum effort to combat the virus.
Beijing's communist leadership has sealed off cities, cancelled flights and closed factories to limit an epidemic roiling the world's second biggest economy to the alarm of global markets and businesses dependent on Chinese supply lines.
The epicentre region of Hubei is in lockdown and the capital Beijing resembles a ghost town.
Deaths in mainland China reached 637 on Friday, with a total of 31,211 cases, WHO chief Tedros Adhanom Ghebreyesus said in Geneva, warning of a worldwide shortage of gowns, masks and other protective equipment.
"For the last two days there had been fewer reported infections in China, which is good news, but we caution against reading too much into that," he told the WHO Executive Board.
"The numbers could go up again."
Virus concerns swiped world markets on Friday, but failed to stand in the way of the best week for stocks since June and the strongest for the dollar since August.
With Chinese buyers rejecting shipments of liquefied natural gas (LNG) due to the epidemic, traders rushed to find alternative locations amid record low prices.
U.S. President Donald Trump, after speaking to Xi by phone, said China was showing "great discipline".
"Nothing is easy, but he will be successful, especially as the weather starts to warm & the virus hopefully becomes weaker, and then gone," Trump said on Twitter.
OPTHALMOLOGIST REBUKED
Ophthalmologist Li was among eight people reprimanded by police in the city of Wuhan, the capital of Hubei, for spreading "illegal and false" information.
His social media warnings of a new "SARS-like" coronavirus - a reference to Severe Acute Respiratory Syndrome, which killed almost 800 people around the world in 2002-2003 after originating in China - angered police.
China was accused of trying to cover up SARS.
Li was made to sign a letter on Jan. 3, saying he had "severely disrupted social order" and was threatened with charges.
Social media users called him a hero and shared a selfie of him lying on a hospital bed wearing an oxygen respirator and holding up his Chinese identification card. One image showed the message "farewell Li Wenliang" etched into snow on a riverbank.
"Wuhan indeed owes Li Wenliang an apology," said Hu Xijin, editor of the government-backed Global Times tabloid.
Rights group Amnesty International called his death a "tragic reminder" of how China's preoccupation with stability made it suppress vital information.
There were signs discussion of his death was being censored.
After briefly trending on Weibo, the topics "the Wuhan government owes doctor Li Wenliang an apology" and "we want free speech" yielded no search results.
"UNACCEPTABLE STIGMA"
The virus has spread around the world, with 320 cases now in 27 countries and regions outside mainland China, a Reuters tally of official statements shows.
WHO emergency expert Mike Ryan called out stigma being attached to the virus amid reports of Asians being shunned in the West. "The unnecessary, unhelpful profiling of individuals based on ethnicity is utterly and completely unacceptable and it needs to stop," he said.
The outbreak could have spread from bats to humans via illegal traffic of pangolins, the world's only scaly mammals, Chinese researchers said, sparking some scepticism.
Two deaths have been reported outside mainland China, in Hong Kong and the Philippines, but how deadly and contagious the virus is remains unclear, prompting countries to quarantine hundreds of people and cut travel links with China.
There were 41 new cases among about 3,700 people quarantined in a cruise ship off Japan, taking the total to 61. Chinese-ruled Hong Kong quarantined for a third day a cruise ship with 3,600 on board.
And about two dozen sick passengers aboard a cruise ship that arrived off New Jersey in the United States were screened for the coronavirus, with four sent to a local hospital out of "an abundance of caution," the local mayor said.
The head of the Beijing Municipal Bureau of Justice, Li Fuying, told reporters that people deliberately concealing contacts or refusing isolation could be punished with death.