SEOUL, May 13 (Reuters) - At least one person confirmed to have COVID-19 has died in North Korea and hundreds of thousands have shown fever symptoms, state media said on Friday, offering hints at the potentially dire scale of country's first confirmed outbreak of the pandemic.

The data represents an unprecedented admission of an "explosive" outbreak in a country that had previously reported no confirmed cases since the pandemic began, and could mark a grave public health, economic, and political crisis for the isolated regime.

Experts said that given North Korea's limited testing capabilities, the numbers released so far probably represent a small fraction of the infections, and could lead to thousands of deaths in one of only two countries in the world without a COVID-19 vaccination campaign.

About 187,800 people are being treated in isolation after a fever of unidentified origin has "explosively spread nationwide" since late April, the official KCNA news agency reported.

Roughly 350,000 people have shown signs of that fever, including 18,000 who newly reported such symptoms on Thursday, KCNA said. About 162,200 have been treated, but it did not specify how many had tested positive for COVID-19.

At least six people who showed fever symptoms have died, with one of those case confirmed to have contracted the Omicron variant of the virus, KCNA said.

Harvard Medical School's Kee Park, who has worked on health care projects in North Korea, said the country has been testing about 1,400 people each week, which is not nearly enough to survey 350,000 people with symptoms.

"What is more worrisome is the sheer number of symptomatic people," he added. "Using a conservative case fatality rate of 1% and assuming the surge is due to an Omicron variant of COVID-19, North Korea can expect 3,500 deaths from this outbreak."