GENEVA (REUTERS) - United Nations (UN) High Commissioner for Human Rights Navi Pillay urged world powers on Tuesday to refer North Korea to the prosecutor of the International Criminal Court (ICC) following a UN report documenting crimes against humanity.

North Korean security chiefs and possibly even leader Kim Jong Un himself should face international justice for ordering systematic torture, starvation and killings comparable to Nazi-era atrocities, UN investigators said on Monday.

"We now need strong international leadership to follow up on the grave findings of the Commission of Inquiry. I therefore call on the international community, in line with the report's recommendations, to use all the mechanisms at its disposal to ensure accountability, including referral to the International Criminal Court," Mr Pillay said in a statement issued in Geneva.

The independent UN investigators, led by Mr Michael Kirby, recommended that the world body refer the situation in North Korea to the Hague-based ICC or set up a special tribunal.

The team also recommended targeted UN sanctions against civil officials and military commanders suspected of the worst crimes. North Korea is already subject to UN sanctions for refusing to give up its atomic bomb programme.

Earlier on Tuesday, China rejected what it said was "unreasonable criticism" of Beijing in the UN report, but it would not be drawn on whether it would veto any proceedings in the Security Council to bring Pyongyang to book.

The UN Human Rights Council, a 47-member state forum that launched the inquiry a year ago, is due to hold a debate on the report on March 17 and vote on its recommendations by March 28.

The United States co-sponsored the commission of inquiry (COI) along with Japan, the European Union and South Korea although, like China, it is not a member of the ICC.

In a statement on Monday, a spokesman for the US State Department said Washington looked forward "to thoroughly reviewing the report and discussing its recommendations with our partners, who share our deep concern about the human rights situation" in North Korea.

The report "provides compelling evidence of widespread and systematic human rights violations" by North Korea, where the rights situation was "among the world's worst", spokesman Jen Psaki said.

"We will continue to work closely with the international community to sustain international attention on the deplorable human rights situation in North Korea beyond the work of the COI," she added.

US Secretary of State John Kerry was in China last week and said after talks in Beijing on Friday that China and the US were discussing specific ways to press North Korea to give up its nuclear programme.

A State Department official said on Tuesday that the US and China agreed on "the fundamental importance of a denuclearised North Korea" but declined to comment on what he said were "private diplomatic conversations".

Western countries and independent experts have accused China of failing to implement properly UN sanctions on North Korea, including punitive measures adopted after Pyongyang's third nuclear test last February.