Read and watch more about North Korea in "March Madness," a VICE News special section on the Hermit Kingdom.

North Korean leader Kim Jong-un and senior officials should be prosecuted for crimes against humanity, the United Nations human rights investigator for the Asian nation said on Monday, criticizing the fact that huge amounts of money was being spent on developing nuclear weapons while many citizens lacked sufficient food or worked in "slave-like conditions." It remains unclear, however, exactly how the international community would bring North Korean leaders to justice.

Political prison camps, torture, "slave-like labor," and religious persecution remain features of the state apparatus, two years after a landmark UN investigation into crimes against humanity, Marzuki Darusman told the UN Human Rights Council.

"The denial of human rights to its citizens internally and this aggressive behavior externally are basically two sides of the same coin. The country is pouring a large amount of resources into developing weapons of mass destruction, while large parts of its population continue to suffer from food insecurity," Darusman said.

"We are now at a crucial stage, therefore there is a fundamental need for countries to make that next step in ensuring accountability is undertaken," he added.

The delegation of the Democratic People's Republic of Korea (DPRK) boycotted the session. The European Union, United States, and Japan supported Darusman's call for accountability, although they did not refer to Kim by name.

Ambassador Robert King, US envoy for North Korea, denounced the "egregious human rights violations committed by the DPRK" and said that the United States would work with other countries to "seek ways to advance accountability for those most responsible."

China, Pyongyang's ally, took a more conciliatory tone, saying human rights issues should not be politicized and calling for a comprehensive approach to dealing with North Korea.

China also rejected Darusman's findings that North Koreans who flee across the border to China were being forced back to their homeland illegally. A report by Darusman, the UN's special rapporteur on human rights in North Korea, submitted recently to the UN's Human Rights Council, noted that under Kim, "persons attempting to flee [North Korea] appear to face harsher treatment than in earlier periods."

Darusman's report said China plays a "critical role" in "bringing concrete and meaningful changes to the situation of human rights" in North Korea.

North Korean Foreign Minister Ri Su-yong, in a speech to the Geneva forum on March 1, said it would boycott any session that examined its record and would "never, ever" be bound by any such resolutions.

Darusman, referring to a report he issued last month, said: "I would like to reiterate my appeal to the international community to move forward to ensure accountability of the senior leadership of the Democratic People's Republic of Korea, including that of Mr. Kim Jong-un."

This could be via the International Criminal Court (ICC) but failing consensus among major powers, North Korea's leadership could be prosecuted in a third country, he said.

He called for the Council to set up a panel of three experts to look into "structure and methods of accountability."

"The question should never be whether to pursue accountability, but rather when and how," Darusman said in his report.

"Individuals who commit crimes against humanity in the DPRK may be held responsible on the basis of customary international law, even though the state is not a party to the Rome Statute of the International Criminal Court and has no provisions against crimes against humanity in its domestic criminal law," Darusman wrote.

The report suggested that, as an alternative to prosecution at the ICC, a third country, such as South Korea, could use the doctrine of "universal jurisdiction" to prosecute North Korean officials for crimes against humanity. The report acknowledged, however, that such an idea had several drawbacks, including the fact that North Koreans would likely not be in custody and would have to be tried in absentia. Additionally, the report said trials in a third country would have "limited impact in restoring trust in the rule of law" in North Korea, and the proceedings would be subject to "possible politicization."

"Despite challenges, prosecution based on the principle of universal jurisdiction might present the only opportunity to move forward on establishing criminal accountability, while the possibility of such prosecution may serve as a catalyst for other processes," the report said.

Most critically, however, the report noted that "current customary international law would not allow the prosecution of a sitting head of state," meaning Kim would be "precluded" from facing charges unless the ICC took up the case.

The report also complained that the UN and the international community have not looked seriously at the various ways North Korean leaders could face charges for crimes against humanity since the first special rapporteur report was published two years ago.

"There has been no comprehensive analysis of which models could be most appropriate," the report said. Darusman urged the ICC to get involved, but noted that the court is only able to handle cases that involve the "the uppermost leadership," which could lead to lower-ranking officials getting off easy. If that happens, the report said, it carries the risk of "entrenching impunity, undermining national legal processes, and fostering resentment and the perception of injustice. It denies victims their right to justice, and may set a dangerous precedent that will have an adverse impact on future stability and the rule of law."

John Fisher of Human Rights Watch said that North Korea had "horrific" forced labor camps, public executions, and a history of mass malnutrition and even "mass starvation."

"Generations of North Koreans have suffered at the hands of the Kim family and its elite," Fisher said.

North Korea follows a "songun," or "military-first" policy, which sees it put a huge amount of resources into the country's military capabilities, at the expense of the welfare of its citizens. It argues that this is necessary because of the ongoing threats from the United States and South Korea.

The country conducted its fourth nuclear test in January and launched a long-range missile the following month.

The latest call for prosecution also comes a day after a North Korean submarine — one of a fleet of around 70 — went missing and is believed to have sunk, according to South Korean and US reports.