North Korea on Sunday reported 15 additional deaths from "fever", days after officially confirming its first-ever Covid-19 cases and ordering nationwide lockdowns.

The outbreak, which leader Kim Jong Un has said is causing "great upheaval", leaves a country with one of the world's worst healthcare systems on the edge of potential disaster.

North Korea has no Covid vaccines, antiviral treatment drugs or mass-testing capacity.

While it has maintained a rigid coronavirus blockade since the pandemic's start, experts have said that massive Omicron outbreaks in neighbouring countries meant it was only a matter of time before Covid snuck in.

Despite activating a "maximum emergency quarantine system" to slow the disease's spread through its unvaccinated population, Pyongyang is now reporting large numbers of new cases daily.

Official state media KCNA on Sunday said 42 people had died since the outbreak's beginning, with 820,620 cases and at least 324,550 receiving medical treatment.

The news agency reported that "all provinces, cities and counties of the country have been totally locked down and working units, production units and residential units closed from each other".

North Korea first revealed the highly contagious Omicron variant had been detected in the capital on Thursday, with Kim ordering nationwide lockdowns after an emergency meeting of the country's Politburo.

"The spread of malignant disease comes to be a great upheaval in our country," Kim said Saturday.

Sunday's KCNA report did not specify whether the new cases and deaths tested positive for Covid-19, but experts say the country will struggle to screen and diagnose on this scale.

North Korea's healthcare system ranked 193 out of 195 countries in a 2021 Johns Hopkins University survey. (AFP)