Hundreds of relieved passengers disembarked a coronavirus-stricken cruise ship in Japan Wednesday after testing negative for the disease that has now claimed more than 2,000 lives in China and spread panic worldwide.

The Diamond Princess has proved a fertile breeding ground for the COVID-19 virus with at least 542 positive cases, and Japan has faced mounting criticism for its quarantine arrangements as the passengers disperse.

"I'm relieved... I want to take a good rest," said a 77-year-old Japanese passenger, who declined to give his name. He said he would be boarding Japan's famously crowded railway system to go home.

Yellow-dotted city buses, plus a dozen or so taxis, were lined up to whisk away the passengers, many of them dragging their luggage behind them and waving to former ship-mates on balconies.

The ship is the biggest cluster outside China, where new figures showed the death toll surging beyond 2,000 with more than 74,000 infected. Hundreds more cases have been reported in two dozen countries.

South Korea reported 15 new confirmed cases -- increasing its total by nearly 50 percent -- including a cluster of at least 11 centred on the southern city of Daegu. Hong Kong reported a second death.

For the 500 passengers disembarking after testing negative, a difficult 14-day quarantine period has come to an end after their dream cruise turned into a nightmare of fear and boredom confined in many cases to small windowless cabins.

"Our last deep gratitude to the crews and captain for such an amazing care... during the epic crisis... we can't wait to see you again soon on board again," tweeted passenger Yardley Wong, who has been cooped up with her six-year-old son.

'Taking its toll'

Those with no symptoms and a negative test received an official certificate saying they posed "no risk of infection".

But not everyone was so lucky.

British passenger David Abel, who became a minor celebrity with his upbeat video messages in the early days of the quarantine -- including a cheeky request to the captain for whisky -- typified the mood shift aboard.

"Mentally, it's now taking its toll. Right now, it's very hard to remain focused on anything," he said.

He later announced he and his wife Sally had tested positive.

China announced Wednesday there were 1,749 new infections, the lowest number of new cases this month. All but 56 new cases were in the epicentre of Hubei province.

Michael Ryan, head of WHO's health emergencies programme, said the outbreak was "very serious" and could grow, but stressed that outside Hubei, it was "affecting a very, very tiny, tiny proportion of people."

But in Japan, some have raised concerns about allowing people from the cruise ship to board flights home or spread out into the notoriously busy Japanese capital.

Kentaro Iwata, a professor at the infectious diseases division of Kobe University, blasted the on-ship quarantine as a "major failure, a mistake".

"It is highly likely secondary infections occurred," Iwata told AFP, saying scepticism from abroad of the quarantine was "only natural".

He later said in a video published online that he was self-quarantining after a brief visit to the ship where he raised major concerns about the procedures on board.

"It was completely chaotic," he said.

'Cheer for them'

Several countries appear to have lost patience with the on-board quarantine and chartered planes to repatriate citizens.

In the first such evacuation Monday, more than 300 Americans flew home even though 14 had tested positive.

Britain, Hong Kong and Australia are among other countries that have vowed to repatriate people from the ship but will insist on a further 14-day quarantine on home soil.

Nathalie MacDermott, a medical expert at King's College London, recommended a further 14-day self-quarantine for those leaving.

"Given the circumstances on board the Diamond Princess, those passengers leaving the boat should be managed in a similar manner to those individuals departing a highly affected city or region," said MacDermott.

South Korea vowed to block foreigners who have been on board the Diamond Princess from entering the country.

Disembarkation is expected to take around three days as more test results become available. The crew will begin a new quarantine when the last passenger has left.

People in Yokohama appeared supportive of the decision to allow the passengers out despite the virus fears.

"I am sure those people on board must be really worried. I hope they can go back to their normal life soon," said 51-year-old Isamu Habiro.

"As a Yokohama resident, I don't want them to be treated unfairly. I want to cheer for them," Habiro told AFP.