SEOUL - After months of denying it had any coronavirus infections, North Korea has reported its first suspected case, blaming an alleged defector who had recently reentered the country.

State media said a runaway who was "suspected to have been infected with the vicious virus" had left for South Korea three years ago but returned July 19 "after illegally crossing the demarcation line" that separates the two Koreas.

The state-run Korean Central News Agency (KCNA) said an "uncertain result was made from several medical checkups of the secretion of that person's upper respiratory organ and blood," but it did not say whether the patient had undergone a coronavirus test.

"The person was put under strict quarantine as a primary step and all the persons in Kaesong City who contacted that person and those who have been to the city in the last five days are being thoroughly investigated, given medical examination and put under quarantine," it said.

North Korean leader Kim Jong Un convened a politburo meeting Saturday during which he acknowledged "the vicious virus could be said to have entered the country," KCNA said.

Kim, the report said, declared a state of emergency in the affected area and "took the preemptive measure of totally blocking Kaesong City and isolating each district and region from the other within July 24 afternoon just after receiving the report on it."

North Korea had long insisted it was coronavirus-free, even though a wide range of outside experts said that was practically impossible. The country shares a long border with China, where the virus originated. Although North Korea moved quickly to formally close the border, much of the interaction across that border is informal and hard to control.

An outbreak in North Korea would be extremely dangerous, since many parts of the country are impoverished and lack an adequate health care system.

International aid groups have sent medical supplies, including face masks and thousands of coronavirus test kits, to North Korea since the worldwide coronavirus pandemic began.

The delivery of that medical aid has been complicated by export controls, border closures and international sanctions on North Korea's nuclear program.

Since the coronavirus emerged last December in China, more than 200 countries have reported cases. Worldwide, nearly 16 million cases of coronavirus have been confirmed, and more than 640,000 people have died.