North Korea's outbreak of suspected COVID-19 cases in the northeastern province of Ryanggang earlier this week was caused by influenza, its state media said Friday.

Earlier, the North said four fever cases suspected of carrying "malignant epidemic" were reported Tuesday in Ryanggang Province bordering China, just two weeks after it declared victory over the coronavirus crisis that began in mid-May.

"According to information from the State Emergency Epidemic Prevention Headquarters, it made clear that all the fever cases that occurred in Ryanggang Province were influenza," the official Korean Central News Agency (KCNA) said.

Health authorities urged people to wear masks and report to relevant authorities without traveling or moving if they show symptoms of fever, saying that influenza can easily occur in all areas of the country.

The fever patients returned back to normal body temperature and the lockdown of the area was lifted, according to the KCNA.

On Aug. 10, North Korean leader Kim Jong-un declared victory over COVID-19 and ordered the lifting of the country's "maximum emergency anti-epidemic" measures. (Yonhap)