Scores of new coronavirus cases and a first death in South Korea raised fears of the global spread of the pathogen as research suggested it was more contagious than thought.
China, where the virus emerged in December, reported a sharp drop in new cases but the data was partly attributable to a change in how it diagnoses the virus.
Coronavirus, known as COVID-19, emerged in the central Chinese city of Wuhan late last year, apparently in a food market, and has now infected some 75,000 people and killed about 2,100.
South Korea confirmed its first death from the virus hours after the mayor of its fourth-largest city urged residents to stay indoors after a spike of more than 40 new infections, most traced to a church attended by a woman who tested positive.
In Japan, two former passengers who tested positive for coronavirus on the Diamond Princess cruise ship have died, authorities there said.
The man and woman, both Japanese and in their 80s, were taken off the cruise ship last week and died in hospital, the first fatalities among the more than 600 passengers and crew who have tested positive for the virus.
The man had a pre-existing condition of bronchial asthma and a history of angina treatment, the health ministry said in a statement, but the woman had no known pre-existing conditions. The direct cause of her death was pneumonia.
Health Minister Katsunobu Kato said they were sent to medical facilities when they showed symptoms.
"I believe that they received the best possible treatment," he added.
The huge vessel moored in Yokohama near Tokyo is the biggest coronavirus cluster outside the Chinese city of Wuhan, which is at the centre of the outbreak, with 634 positive cases, including 13 further people confirmed today, among the passengers and crew.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
Read More:
'No surprise' if coronavirus case confirmed in Ireland
Trapped at home: Irishman's virus lockdown experience
Coronavirus: Your questions answered
Yesterday, 443 passengers disembarked after testing negative for the COVID-19 virus and not showing symptoms during a 14-day quarantine period. The removal of all passengers was expected to take at least three days.
More passengers left the ship today, packing into yellow buses and leaving for stations and airports to head home.
But questions are increasingly being asked as to why former Diamond Princess passengers are able to roam freely around Japan's famously crowded cities, even if they have tested negative.
"Is it really safe to get off?" screamed a headline in the Nikkan Sports tabloid.
The paper quoted one passenger who said he was tested on 15 February, but only left four days later.
"I thought I could be infected during the four days. I thought 'Is it really OK'?"
The Diamond Princess was quarantined on 5 February when a passenger who left ship in Hong Kong tested positive for the virus.
Passengers were confined to cabins except for brief trips on deck wearing masks and gloves, when they were told to keep their distance from others.
Japanese authorities have defended their quarantine procedures, stressing that risky and safe areas were strictly divided and there was a station installed for safely removing contaminated gear.
"We've been doing our best in the circumstances," Mr Kato told MPs.
"I want you to understand that not only our officials at the health ministry but also Self-Defence Forces officials and medical officials are working desperately hard," he added.
The government also released a document from the National Institute of Infectious Diseases (NIID), which pointed to "clear evidence that substantial transmission of COVID-19 had been occurring prior to implementation of quarantine on Diamond Princess".
The report concluded that: "Quarantine intervention was effective in reducing transmission among passengers."
The NIID also noted the unique situation faced by Japanese authorities.
"Due to the nature of the ship, individual isolation of all those aboard was not possible. Sharing of cabins was necessary, and some crew had to continue to perform essential duties for the functioning of the vessel."
The 1,045 crew members on board are expected to endure a further 14-day quarantine after the last passenger has disembarked.
Several countries have evacuated their citizens from the ship and insisted they undergo a further 14-day quarantine when they arrive on home soil.
The Department of Foreign Affairs said its embassy in Tokyo is in ongoing contact with Irish citizens, who were on the ship, regarding their consular needs.
In a statement, the department said it is working with EU partners and other like-minded countries regarding options for their onward travel.
Two Irish citizens who were on board the Diamond Princess and tested positive for COVID-19 are continuing to receive treatment in hospital in Japan.
Outside the Diamond Princess, Japan has seen 84 cases.
Today, the Health Service Executive added the virus to their list of notifiable diseases but said there is no confirmed case of COVID-19 in Ireland.
South Korea coronavirus cases spike as infection spreads in sect
A cluster of coronavirus infections centred on a sect in the South Korean city of Daegu leaped to 39 cases, with its mayor advising residents to stay indoors as the country's total spiked for the second successive day.
The first death in the country has also been confirmed.
Almost half the country's patients are linked to a 61-year-old woman who is a member of the Daegu branch of the Shincheonji Church of Jesus.
She first developed a fever on 10 February but reportedly twice refused to be tested for coronavirus on the grounds that she had not recently travelled abroad, and attended at least four services before being diagnosed.
So far 37 other members of the sect have been confirmed as infected, and the woman is also believed to have contaminated another person at a hospital.
Shincheonji claims that its founder Lee Man-hee has donned the mantle of Jesus Christ and will take 144,000 people with him to Heaven, body and soul, on the Day of Judgement.
Daegu's municipal government said 1,001 Shincheonji members who were believed to have attended the same services as the woman had been asked to self-quarantine.
A total of 43 cases have been confirmed in the city and neighbouring North Gyeongsang province, and Daegu mayor Kwon Young-jin urged residents: "Starting from today, please refrain from leaving your house as much as possible."
The emergency units at all four general hospitals in Daegu have been closed as a precaution, a city official said.
Additional reporting Fergal Bowers
