One of North Korea’s most senior diplomats warned on Monday that if any effort was made to charge the country’s leader, Kim Jong-un, with crimes against humanity at the International Criminal Court, the North would take unspecified “countermeasures.”

The United Nations envoy, Jang Il-hun, also denied that the country had political prisoners.

The statements by Mr. Jang came in a rare and sometimes heated hourlong discussion of the country’s reaction to a United Nations report in February — which included satellite photographs of a network of prison camps, and interviews with dissidents who had escaped from them — as well as North Korea’s nuclear policies. While he hewed to Pyongyang’s official talking points about the report, he did not rule out allowing outside inspectors to visit the sites in the future.

“In my country we don’t even know the term ‘political prisoners,’ ” Mr. Jang, a 32-year veteran of the North Korean Ministry of Foreign Affairs, said in a session with about 40 members of the Council on Foreign Relations. He insisted that the camps in the satellite photographs were “reformatories” and denied that anyone had been forced into labor. “It is a normal prison,” he added.

That was not the conclusion of the Commission of Inquiry on Human Rights in the Democratic People’s Republic of Korea, which was created by the United Nations Human Rights Council. In its report, the commission detailed conditions in the camps and concluded in its February report that “these crimes against humanity entail extermination; murder; enslavement; torture; imprisonment; rape, forced abortions and other sexual violence; persecution on political, religious, racial and gender grounds; the forcible transfer of populations; the enforced disappearance of persons; and the inhumane act of knowingly causing prolonged starvation.”