The impoverished nation has been behind a rigid blockade since early last year to protect itself from the pandemic, with the economy suffering and trade with key partner China dwindling to a trickle.

In June, state-run KCTV admitted North Korea was facing a "food crisis", sounding the alarm in a country with a moribund agricultural sector that has long struggled to feed the population.

The same month, leader Kim Jong Un said the food situation was "getting tense".

Ordinary North Koreans are "struggling on a daily basis... to live a life of dignity", and the worsening humanitarian situation could "turn into a crisis", Tomas Ojea Quintana, UN special rapporteur on human rights, said in his latest report.

Pyongyang is under multiple sets of international sanctions over its nuclear and ballistic missile programmes, which have seen rapid progress under Kim.

Quintana said such restrictions should be eased to protect the country's most vulnerable in the face of a severe food shortage.

"The most vulnerable children and elderly are at risk of starvation," he said.

"Sanctions imposed by the UN Security Council should be reviewed and eased when necessary to both facilitate humanitarian and lifesaving assistance."

The report comes about three months after the UN's Food and Agricultural Organisation said North Korea was facing a food shortage of around 860,000 tonnes this year, and could experience a "harsh lean period".

Pyongyang has stayed away from talks on its nuclear programme since the collapse of a second summit between Kim and then US president Donald Trump in Hanoi and has rebuffed South Korean efforts to revive dialogue.

Under President Joe Biden, the United States has repeatedly declared its willingness to meet North Korean representatives, while saying it will seek denuclearisation.

But this week Kim blamed Washington for tensions on the peninsula, and insisted Pyongyang's weapons were for self-defence and not aimed at any particular country.