North Korea's development of nuclear weapons technology poses a major threat to international security, but it seems that its weapons program is receiving help from abroad.

Ken Kato, director of Tokyo-based Human Rights in Asia and a member of International Coalition to Stop Crimes Against Humanity in North Korea, is alleging that a scientist with links to North Korea is working at a Japanese university on technology required to achieve miniaturization of nuclear warheads.

In response, Kato has informed ambassadors from each of the UN Security Council member states, calling on them to close what he says is a glaring loophole in the global ban on the transfer of nuclear technology to North Korea.

The rule in question is paragraph 17 of UN Resolution 2270, which bans specialized nuclear and missile-related teaching or training only to those identified as "DPRK nationals." According to Kato, that wording permits North Koreans living in Japan who sympathize with the regime in Pyongyang to get around the ban.

"There are six ethnic Korean scientists living in Japan sanctioned by the Japanese government for their involvement in North Korea's espionage activities," Kato told DW. "At least two of them hold South Korean passports, even though they support the North Korean regime and belong to the North Korea-affiliated Korean Association of Science and Technology in Japan."

N. Korea is widely suspected of trying to develop miniature nuclear warheads

Kato added that there are tens of thousands of ethnic Koreans living in Japan who support the North Korean regime but have obtained South Korean passports and travel abroad as South Korean citizens.

Accusations

In his letter to the UN Security Council, Kato singled out Dr. Pyeon Cheol-ho, an assistant professor at Kyoto University's Research Reactor Institute, as an example of North Korea's "nuclear spies" operating in Japan.

"Dr. Pyeon received grants from the Kim Man Yu Science Foundation for research on nuclear testing in 1997 and 1999," said Kato, adding that the foundation is "closely linked to the North Korean regime" and one of its directors, Yang Soo-jeong, is "a member of North Korea's Supreme People's Assembly."

Quoting experts, Japanese media have reported that Dr. Pyeon's research on neutrons could be used to achieve the miniaturization of nuclear warheads - an area to which North Korea is devoting a great deal of effort as it tries to master the technology required to mate a nuclear warhead with an intercontinental ballistic missile.

It has also been reported that Dr. Pyeon visited North Korea on seven occasions between 1992 and 2008, although he has denied those claims.

Support for the North from abroad

Protests against Chongryon in Tokyo after a 2013 N.Korean nuclear test

There are presently an estimated 610,000 people of Korean origin living in Japan. Many are descendants of forced laborers brought here during Japan's colonial occupation of the Korean Peninsula.

Around 150,000 still swear allegiance to the regime of Kim Jong Un in Pyongyang and there have been numerous allegations that Chongryon, the association for North Korean residents of Japan, has been involved in illegal activities designed to aid the North.

These range from illegally transferring funds to North Korea to involvement in the kidnapping of Japanese nationals, espionage, tax evasion and the illegal procurement of advanced technology to be used in engineering projects, such as missiles.

"Clearly, 'zainichi' Koreans [those descended from immigrants] are divided between those who support the North and those who side with the South," Jeff Kingston, director of Asian Studies at the Japan campus of Temple University, told DW.

"And there are undoubtedly some who continue to have sympathy for the North and serve as a major source of funds for the regime," he added. "It would come as no surprise to me if a North Korean here was engaged in research related to nuclear energy, although I would want to see more evidence in individual cases."

North Korean education in Japan

Kato pointed out that Dr. Pyeon studied at a North Korean-affiliated high school in Japan and was a member of the Korean Youth League, which required him to study North Korean ideology. His parents were both members of Chongryon. Kato also alleges that Pyeon's father-in-law was involved in the abduction of a Japanese citizen in 1978.

Kato claims that the Japanese authorities "are well aware" of Dr. Pyeon's activities, but would find it difficult to prove the allegations against him in a court of law without revealing sources and classified information.

"I am sure Dr. Pyeon is not hiding a shortwave transmitter in his attic, like in the old spy movies, because he does not need one," Kato said. "It is absolutely vital that the Security Council prohibits nuclear and missile-related research by individuals who are associated with the North Korean regime."

Contacted by phone, Dr. Pyeon declined to comment on questions about Kato's allegations.

"We have to stop this sort of nuclear and industrial espionage in Japan as quickly as possible," Kato said. "In the 1950s, the US hanged Julius and Ethel Rosenberg for being nuclear spies. And now, nuclear weapons are in the hands of the world's most unpredictable and unstable dictator, who could use them on a whim. It is ridiculous that we have nuclear and industrial spies on the loose in Japan."