The number of people killed by the new coronavirus rose by 97 on Sunday, the highest number of casualties in a day.
The total number of deaths in China is now 908 - but the number of newly-infected people per day has stabilised.
Across China, 40,171 people are infected while 187,518 are under medical observation.
Meanwhile, 60 more people have tested positive on a cruise ship quarantined in Japan - meaning 130 out of 3,700 passengers have caught the virus.
The Diamond Princess ship is on a two-week quarantine off Yokohama, after a passenger - who earlier disembarked in Hong Kong - tested positive.
The infected passengers are taken off board and treated in nearby hospitals.
The new cases mean around a third of all coronavirus patients outside of China were on the Diamond Princess.
According to Chinese data, 3,281 patients have been cured and discharged from hospital.
On Monday, millions of people returned to work after the Lunar New Year break, which was extended from 31 January to curb the spread of the virus.
But precautionary measures remain in place, including the staggering of working hours, and the selective reopening of workplaces.
Over the weekend, the number of coronavirus deaths overtook that of the Sars epidemic in 2003 which also originated in China and killed 774 people worldwide.
The WHO on Saturday said the number of new cases in China was "stabilising" - but warned it was too early to say if the virus had peaked.
On Sunday evening, the organisation sent an international mission to help coordinate a response to the outbreak.
The new virus was first reported in Wuhan, the capital of Hubei province. The city of 11 million has been in lockdown for weeks.
The outbreak was declared a global emergency by the WHO on 30 January.
It has spread to at least 27 other countries and territories, but so far there have only been two deaths outside of mainland China, in the Philippines and Hong Kong.
The director-general of the WHO on Sunday warned that the virus being transmitted by people who have not been to China could be the "tip of the iceberg".
"There've been some concerning instances of onward 2019nCoV spread from people with no travel history to China," Tedros Adhanom Ghebreyesus wrote on Twitter
"The detection of a small number of cases may indicate more widespread transmission in other countries; in short, we may only be seeing the tip of the iceberg."
Meanwhile in Hong Kong, passengers on a quarantined cruise ship have been allowed to disembark after tests showed no infection among them or its crew.
The World Dream had been held in isolation after eight passengers from a previous cruise had caught the virus.
South Korea has issued a temporary ban on cruise ships entering its ports due to fears of spreading the virus.