South Korea says the number of new coronavirus cases in the country has more than has doubled in one day.
Officials said on Saturday that 229 new cases had been confirmed since Friday, raising the total to 433.
Vice Health Minister Kim Gang-lip said the outbreak had entered “a serious new phase”.
Many of the new cases are linked to a hospital and to a religious group near the south-eastern city of Daegu, authorities have said.
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Two patients in South Korea have died so far and there are fears the number will rise.
Daegu and nearby Cheongdo – where the hospital is situated – have been declared “special care zones” and the streets of Daegu are reported to be largely abandoned.
The latest developments came as Chinese health authorities reported a decrease in deaths and new cases of the coronavirus on Saturday.
The head of the World Health Organization (WHO), Dr Tedros Adhanom Ghebreyesus, has expressed concern at the number of new cases with no clear link to China or other confirmed cases.
He warned that the window of opportunity to contain the virus was “narrowing”.
China has reported 76,288 cases including 2,345 deaths, while more than 1,200 cases of the virus have been confirmed in 26 other countries and there have been eight deaths, the WHO says.
A cruise ship, The Diamond Princess, has been quarantined off the coast of Japan with more than 600 confirmed cases of the virus.
An evacuation flight carrying 32 British and other European passengers has taken off from Japan and is due to land in England later on Saturday.
On Friday, doctors in Italy said a 78-year-old man became the first person in the country to die from the new coronavirus, Ansa news agency reports.
Earlier Italy had announced 16 more cases and its health minister said schools and offices would be closed and sports events cancelled in the affected regions.
The new virus, which originated last year in Hubei province in China, causes a respiratory disease called Covid-19.