North Korean leader Kim Jong-un chastised top ruling party officials for failures in anti-epidemic work that led to an unspecified "grave incident" and put the safety of the country and people at risk, state media reported on Wednesday.

The report by state news agency KCNA did not elaborate on what happened, or how it put people at risk.

North Korea has not officially confirmed any Covid-19 cases, a claim questioned by South Korean and US officials. But the reclusive country has imposed strict anti-virus measures, including border closures and domestic travel curbs.

Kim called a meeting of the Workers’ Party of Korea politburo to address some party executives’ neglect of duty, including failing to implement important long-term measures to fight the pandemic, KCNA said.

"The General Secretary pointed out … a grave incident that created a major crisis for the safety of the country and people and the serious consequences that resulted from it," the report said.

Several politburo members, secretaries of the central committee, and officials of several state agencies were replaced at the meeting, though KCNA did not specify if the shakeups were related to the neglect of pandemic-related duty.

Last year, North Korea said it had declared a state of emergency and locked down the border city of Kaesong after a person who defected to South Korea three years ago returned across the fortified border with what state media said were symptoms of Covid-19.

The World Health Organisation later said North Korea’s coronavirus test results for the man were inconclusive.