Two Japanese passengers who contracted the Covid-19 virus on board a cruise ship quarantined in Japan have died.

One passenger died from Covid-19, while the other died from pneumonia, said local reports. Both were in their 80s and had underlying health conditions.

They were being treated in hospitals after being taken off the Diamond Princess last week.

At least 621 people on the ship tested positive for the virus, the biggest cluster outside China.

Japan's health minister said both passengers had been sent to medical facilities after showing symptoms. 

"I believe they received the best possible treatment", Katsunobu Kato added.

The Diamond Princess was carrying 3,700 people in total and passengers who tested negative for the virus began leaving the ship on Wednesday after a 14-day quarantine.

Hundreds have now disembarked from the cruise. Others are set to leave over the next two days.

More than 150 Australian passengers have already arrived in Darwin, where they will begin two weeks of quarantine.

The first batch of people from Hong Kong have also flown back to the city, where they will similarly be quarantined.

UK Foreign Secretary Dominic Raab said the 74 Britons on board the ship would be flown home on Friday. Indonesia is also set to repatriate its citizens.

But there are fears and criticism over Japan's handling of the quarantine on the Diamond Princess.

Japanese health expert Kentaro Iwata, professor at the infectious diseases division of Kobe University, visited the Diamond Princess and said the situation on board was "completely chaotic".

"The cruise ship was completely inadequate in terms of infection control," he said in a widely shared YouTube video which he has since taken offline.

US officials have also said moves to contain the virus "may not have been sufficient".

But on Thursday, Mr Kato responded to Mr Iwata's criticism, saying authorities had worked hard to deal with a very complicated situation.

"We've been doing our best in the circumstances," Mr Kato told Japanese lawmakers.

"Not only our officials at the health ministry but also Self-Defence Forces officials and medical officials are working desperately hard.

"We have specialists of infectious diseases [on the ship], and we get feedback from them about our operation every day, including dividing [the areas inside the ship]."

The health minister stressed that the cruise ship was "not a well-established place such as a hospital", and that the authorities "kept correcting" various problems on a daily basis.

"We have to examine and learn from this case because we think this is a global issue," Mr Kato said.

On Wednesday, Japan's National Institute of Infectious Diseases (NIID) released its report, which pointed to "clear evidence that substantial transmission of COVID-19 had been occurring prior to implementation of quarantine on Diamond Princess 5 February".

"The decline in the number of confirmed cases, based on reported onset dates, implies that the quarantine intervention was effective in reducing transmission among passengers," the report said.

New infections in China declining

China, where the outbreak began, has seen a sharp drop in the number of new infections.

There were 394 new confirmed cases and 114 deaths reported on Wednesday, down from 1,749 new cases on Tuesday, the National Health Commission said.

Overall, there have now been 2,118 deaths and nearly 75,000 confirmed infections recorded in mainland China. Officials say 16,155 patients have recovered.

There are more than 1,000 cases outside of China with the biggest cluster on the Diamond Princess in Japan, followed by Singapore, South Korea and Hong Kong.

Iran says two people infected with the virus have died in the city of Qom - the first reported deaths in the Middle East.

On Wednesday, Hong Kong said a 70-year-old man with underlying illnesses became the territory's second fatality.

France, Japan, the Philippines and Taiwan have each had one death attributed to the virus.

Sharp rise in South Korea

South Korea on Thursday announced a jump of 31 confirmed Covid-19 infections - 23 of them from a newly identified cluster at a large religious community. South Korea now has a total of 82 confirmed cases.

The cluster is in the south-western city of Daegu - home to 2.5 million residents - and is believed to be linked to a 61-year-old woman who was confirmed to be infected earlier this week.

The Korean Centre for Disease Control said the woman had had contact with 166 people, who were asked to self-quarantine, South Korea's Yonhap news agency reports.

The religious sect known as the Temple of the Tabernacle of the Testimony, which has been accused of being a cult, said it had shut down its Daegu branch and that services in other regions would be held online or individually at home.

The mayor of the city has described the event as an "unprecedented crisis" and urged people in the city to stay indoors. BBC

Coronavirus: First passengers disembark from Diamond Princess in Japan

Some Diamond Princess passengers are being allowed to leave if they have tested negative for Covid-19.

Thua Thien-Hue: No nCoV infection 14 days after visit of Diamond Princess cruise

The People’s Committee of the central province of Thua Thien – Hue on February 11 said there is no infection with NCoV in the province during 14 days after the arrival of Diamond Princess cruise ship at Chan May port on January 27.