Japan is only using a sixth of its capacity to test for the coronavirus even as it is increasing its ability to do so, government data shows, adding to concern it is understating its outbreak and not doing enough to contain it.

Nationwide capacity for the polymerase chain reaction (PCR) test has grown to 7,500 a day, on track to reach 8,000 a day target by the end of the month.

But the number of tests conducted has been on average 1,190 a day over the past month, for a total of 32,125, according to health ministry data.

That compares with more than the 200,000 tests conducted in South Korea and the 80,000 in Italy.

The ministry says it has made it easier for doctors to order the PCR tests, so the figures for the number of tests carried out reflects the discretion of physicians.

"Just because you have capacity, it doesn't mean that we need to use that capacity fully," health ministry official Yasuyuki Sahara told a news briefing on Tuesday.

"It isn't necessary to carry out tests on these people who are just simply worried."

Japan has had 868 confirmed cases of the coronavirus and 29 related deaths, not including cases from the Diamond Princess cruise ship, according to public broadcaster NHK.

The virus has infected more than 180,000 people and killed almost 8,000 globally with the most serious spread now taking place in

Europe after China, where the virus originated late last year, brings its epidemic under control.

While Japanese doctors have carried out more than 32,000 tests, only 16,484 people have actually been tested, given that many are often tested multiple times.

World Health Organization (WHO) head Tedros Adhanom Ghebreyesus has said countries need to boost testing. "We have a simple message for all countries: test test test. Test every suspected case," he said.

Japan's health ministry has been focusing on clusters of cases, with the biggest around the megacities of Osaka and Tokyo, and in the prefectures of Hyogo, Hokkaido and Aichi.

The ministry's latest cluster map shows 13 such groupings across the country.

With the rate of testing low, unseen clusters may be "rapidly increasing where containment is failing", said Kenji Shibuya, director of the

Institute for Population Health at King's College London.

To increase surveillance without overtaxing hospitals and doctors, Japan should introduce the type of drive-through testing that South Korea has implemented, Shibuya said.

Japanese health authorities have said there was no need for drive-through testing, although NHK reported on Tuesday that health minister Katsunobu Kato said he was open to the idea as a way to keep infected people out of hospital waiting rooms.

The United States and most of Europe have enacted travel bans and put major cities on lockdown to slow the spread of coronavirus.

Japan has closed schools and canceled many sporting events, but has refrained from forcing travel, businesses and restaurants to shut.

Sahara said more containment measures may be announced after a meeting on Thursday of infectious diseases experts who have been advising the government.

"We are conducting investigations, collecting data, and based on which, we have consultation with experts to make a decision or judgment," Sahara said.

"So it isn't that we are complacent or we are optimistic."

Reuters