GENEVA (Reuters) - A U.N. expert on human rights in North Korea has asked the United Nations to officially notify North Korean leader Kim Jong Un that he may be investigated for crimes against humanity.

North Korean leader Kim Jong Un salutes during a visit to the Ministry of the People's Armed Forces on the occasion of the new year, in this undated photo released by North Korea's Korean Central News Agency (KCNA) on January 10, 2016. REUTERS/KCNA

A landmark 2014 report on North Korean human rights, co-authored by Marzuki Darusman, concluded that North Korean security chiefs and possibly Kim himself should face justice for overseeing a system of Nazi-style atrocities.

Pyongyang has consistently brushed off the allegations and rejected any responsibility for human rights violations.

In a report to the U.N. Human Rights Council, Darusman recommended that the Council arrange an official communication, sent directly to Kim and signed by Darusman or U.N. High Commissioner for Human Rights Zeid Ra’ad al-Hussein.

“(It should) advise him and other senior leaders that they may be investigated and, if found to be responsible, held accountable for crimes against humanity committed under their leadership,” Darusman wrote.

His report, dated Jan. 19 but published on Monday, also said three experts should be appointed to find the best legal path to hold North Korea to account and find “creative and practical” ways to establish the truth and ensure justice for victims.

Darusman stressed the importance of using the International Criminal Court but said it was “able to handle only the uppermost leadership”.

Only the U.N. Security Council can involve the court, but North Korea’s sole ally, China, a veto-wielding member of the top U.N. body, has repeatedly rejected calls for the Security Council to tackle human rights in North Korea.

However, China said on Friday it would back a U.N. resolution to make North Korea “pay the necessary price” for recent North Korean rocket launches, with the aim of bringing Pyongyang back to the negotiating table.

Darusman’s report, which will be considered by the Human Rights Council next month, said the human rights situation in North Korea did not appear to have improved.

However, he said that last September North Korea had invited Zeid to visit and expressed interest in continuing discussions on technical assistance from the U.N. human rights office.