SEOUL, South Korea (AP) — North Korea said Friday six people died and nearly 190,000 are under quarantine following a rapid spread of fever across the nation in recent weeks, a day after it first acknowledged a COVID-19 outbreak in a largely unvaccinated population.

The North’s official Korean Central News Agency said Friday that more than 350,000 people were treated for fever that “explosively” spread nationwide since late April and that 162,200 people recovered. It said said 187,800 people are being isolated for treatment after 18,000 people were newly found with fever symptoms on Thursday alone.

It wasn’t immediately clear how many of the cases were COVID-19 and the country likely lacks testing supplies. The North said one of the six people who died was confirmed to have been infected with the omicron variant.

North Korea imposed a nationwide lockdown on Thursday to control its first acknowledged COVID-19 outbreak after maintaining a widely doubted claim for more than two years that it completely fended off the virus that has spread to nearly every place in the world.

State media said tests of virus samples collected Sunday from an unspecified number of people with fevers in the capital, Pyongyang, confirmed they were infected with the omicron variant. The reports did not specify the number of cases.

Hours after North Korea confirmed the outbreak Thursday, South Korea’s military said it detected the North firing three short-range ballistic missiles toward the sea in what possibly was a show of strength after leader Kim Jong Un publicly acknowledged the virus outbreak.

It was the North’s 16th round of missile launches this year as it pushes a brinkmanship aimed at forcing the United States to accept North Korea as a nuclear power and negotiate sanctions relief and other concessions from a position of strength.

Experts say a failure to slow coronavirus infections could have serious consequences because the country has a poor health care system and its 26 million people are believed to be mostly unvaccinated.

KCNA said Kim was briefed over the fever during his visit state emergency epidemic prevention headquarters on Thursday and criticized officials for failing to prevent “a vulnerable point in the epidemic prevention system.”

He said the spread of the fever has been centered around capital Pyongyang and nearby areas and underscored the importance of isolating all work, production and residential units from one another while providing residents with every convenience in curbing the spread of the “malicious virus.”

“It is the most important challenge and supreme tasks facing our party to reverse the immediate public health crisis situation at an early date, restore the stability of epidemic prevention and protect the health and wellbeing of our people,” KCNA quoted Kim as saying.