* Rights campaigners feared Beijing would shield Pyongyang
* Report accused North Korea of Nazi-style atrocities
* China says report unfounded, "divorced from reality"
* Chief investigator Kirby convinced of prosecutions someday (adds quotes from press conference, new paragraphs 6-8, 13)
By Tom Miles and Stephanie Nebehay
GENEVA, March 17 (Reuters) - China dismissed on Monday a U.N. report alleging North Korea has committed crimes against humanity, effectively confirming the fears of human rights advocates that Beijing will shield its ally from international prosecution.
The report, published in February, accused the reclusive country of mass killings and torture comparable to Nazi-era atrocities and said officials, possibly even Supreme Leader Kim Jong Un himself, should face the International Criminal Court (ICC).
Chen Chuandong, a counsellor at China's mission in Geneva, told the U.N. Human Rights Council that the independent commission of inquiry had made unfounded accusations and recommendations that were "divorced from reality".
"The inability of the commission to get support and cooperation from the country concerned makes it impossible for the commission to carry out its mandate in an impartial, objective and effective manner," Chen said.
China, as a member of the U.N. Security Council, would have the power to veto any move to refer North Korea to the Hague-based ICC. Diplomats had already warned China was likely to object to the report, which also criticised Beijing for its treatment of North Korean defectors.
But Michael Kirby, chief author of the report, said he was convinced North Korea's leadership would eventually face the ICC for crimes documented in the commission's archives, which hold the testimonies of hundreds of witnesses.
"I have lived long enough to see things that looked impossible come to full fruit," Kirby told a news conference.
"The independence of East Timor, the independence of the Baltic states and other steps following the fall of the Berlin Wall are all indications that things can happen that don't look certain now. They won't meet media deadlines but they will occur."
Kirby, a retired Australian judge, had opened the debate by challenging the United Nations to take action.
"Contending with the scourges of Nazism, apartheid, the Khmer Rouge and other affronts required courage by great nations and ordinary human beings alike," he said.
"It is now your solemn duty to address the scourge of human rights violations and crimes against humanity in the Democratic People's Republic of Korea."
STARVATION AND MISTREATMENT
Kirby said the findings were unequivocal, and demanded closure of political prison camps believed to hold up to 120,000 people, many suffering "starvation and mistreatment".
"They are required to live on rodents, and on particular kinds of grass if they can get it, on lizards and other sources of protein. The numbers who die of starvation is very high."
But Chen said the report was based on information and interviews collected outside the country, without first hand information. "The question then arises: can such an inquiry be truly credible?"
Shin Dong Hyuk, a North Korean born in a political prison camp who escaped after his mother and brother were executed, told Reuters he had expected China to reject the report.
But the "big purpose" of establishing the inquiry was to get the report discussed at the U.N. Security Council, he said.
In a speech at the debate, he said millions of people had been killed in Nazi concentration camps during World War Two.
"And 60 years later, at this moment in North Korea, hundreds of thousands of political prisoners are waiting for their death," he said.
U.S. Ambassador Robert King, the U.S. envoy on North Korean human rights issues, said pressure on Pyongyang would go on even if China blocked a U.N. Security Council resolution.
"The fact that right now we may not be able to go forward as far as we'd like to go does not mean that we're going to stop and say we can't do anything more, and we're not going to do it," he told reporters.
North Korean Ambassador So Se Pyong reiterated Pyongyang's rejection of the report, rejecting it as a ridiculous provocation and a fabrication instigated by the United States and other "hostile forces", who he said should be investigated for their own human rights records. (Reporting by Tom Miles and Stephanie Nebehay; Editing by Tom Heneghan)