North Korean authorities have ordered a five-day shutdown of the capital Pyongyang due to the spread of disease.
The city's residents must stay home between Wednesday and Sunday and during that time are tested for fever several times a day, South Korean NK News reports.
Covid-19 is not mentioned, but according to NK News, the measures include reducing the spread of what is described as the common cold.
It is not known if similar measures have been taken in other parts of the country.
Winter is described as harsh in North Korea with temperatures around minus 22 degrees in Pyongyang.
The usually tightly closed North Korea has been even more closed since the start of the pandemic. The country acknowledged its first outbreak of the virus in April last year but declared victory over it just three months later, calling it a "miracle".
North Korean claims of Covid are strongly disputed by experts and the number of deaths and cases of infection is believed to be greatly understated.
The country is considered to have one of the world's worst healthcare systems, with poorly equipped hospitals, few intensive care units and no drugs or vaccines against covid-19, experts say.
Few of the country's 25 million inhabitants are believed to be vaccinated.