A UN Commission of Inquiry has found that crimes against humanity have been committed in North Korea and will call for an investigation by the International Criminal Court (ICC), the Associated Press news agency has reported.

The report, to be released on Monday, is the most authoritative account yet of rights violations by North Korean authorities, and is bound to infuriate its unpredictable leader. But justice remains a distant prospect, not least as North Korea's ally, China, would be likely to block any referral to the Hague-based ICC.

The commission says it has evidence of an array of crimes, including "extermination," crimes against starving populations and a widespread campaign of kidnapping in South Korea and Japan.

The conclusions of the year-long inquiry are due to be released on Monday but the AP reported it had been made aware of its contents ahead of publication.

The news agency said that an outline of the report was provided to it by someone familiar with it, who spoke on condition of anonymity because the source was not authorised to divulge the information before its official release.

A US official, speaking anonymously for the same reason, confirmed the main conclusions, the news agency reported.

The report refers to murder, enslavement, torture, imprisonment, rape, forced abortion, sexual violence, forcible transfers and forced disappearances, and persecution on political, religious, racial and gender grounds.

It also cites an overall system of political repression - the "songbun" class system - that discriminates against North Koreans on the basis of their family's perceived loyalty to the regime.

Outside pressure

The UN has not yet confirmed its accuracy but North Korea's UN mission has rejected the reported findings.

The document, AP says, does not talk in detail of individual responsibility but recommends steps towards accountability.

It concludes that the testimony and other information it received, "create reasonable grounds ... to merit a criminal investigation by a competent national or international organ of justice," AP said.

The commission, the news agency reported, recommended the UN Security Council refer its findings to the International Criminal Court.

Its publication could pile international pressure on North Korea, whose rights record has drawn less censure at the UN than its nuclear and missile programmes.

The secretive country's hereditary regime, however, has shrugged off years of continuous outside reproach, including tough UN and US sanctions directed at its weapons programmes.

'Politically-motivated'

The three-member commission, led by retired Australian judge Michael Kirby, was set up by the UN's top human rights body in March 2013.

It conducted public hearings with more than 80 victims and other witnesses in Seoul, Tokyo, London and Washington, but was not allowed into North Korea itself.

As well as speaking to defectors, the commission heard from experts about a network of camps, estimated to hold 80,000 to 120,000 political prisoners, and about access to food in a country where many children suffer from malnutrition.

When the UN Human Rights Council authorised the commission to begin its work, North Korea denounced it as politically-motivated by "hostile forces" trying to discredit it and dismantle its socialist system.