A Japanese man has recently been taken into custody in North Korea, government officials said Saturday as Tokyo tried to obtain information on the case.

According to informed sources, the man, in his 30s, was visiting the communist regime on a package tour organized by a foreign tourist agency. He was in Nampo, a port town in the western part of the country, the source said.

Japanese officials are concerned his detention could affect negotiations on the long-running abduction issue, which concerns Japanese who were kidnapped by North Korean agents in 1970s and 80s. Five were returned several years ago after talks held under the administration of Junichiro Koizumi.

“North Korea may use the man it has held as a bargaining chip for negotiations with Japan,” an official said.

Prime Minister Shinzo Abe has been trying to arrange a meeting with North Korean leader Kim Jong Un in the wake of the historic summit between North Korea and the United States, but there are no signs of progress yet.

A Foreign Ministry official declined to provide specifics on the case, such as the purpose of the man’s visit, saying only that the ministry is in the process of confirming the details.

Tokyo has reportedly called on Pyongyang to release the man through diplomatic channels, including the North Korean Embassy in Beijing, the sources said. The ministry has asked Japanese to refrain from traveling to North Korea as part of its economic sanctions on the country.

North Korean Foreign Minister Ri Yong Ho did not respond to questions on the matter when he arrived at Beijing international airport Saturday following a trip to Singapore and Iran.

In 1999 a Japanese newspaper reporter working in North Korea was taken into custody on spy charges and detained for about two years.

Sources familiar with bilateral relations said last month that North Korea has established a team to negotiate with Japan, which itself is seeking direct talks to settle various issues. The team was apparently established sometime between April and the historic U.S.-North Korea summit on June 12, reflecting a move by Pyongyang to explore dialogue with Tokyo amid the rapidly changing geopolitical situation on the Korean Peninsula.

North Korea judged earlier this year that mending ties with Japan would become a future task if it moves to improve ties with the United States, South Korea and China, the sources said.

At a plenary meeting in April of the central committee of North Korea’s ruling party, the policy of pursuing active dialogue with surrounding countries was adopted, they added.

Tokyo has long sought answers about the abduction issue. Japan officially lists 17 citizens as abduction victims and suspects the North’s involvement in many more disappearances.

But no substantial progress has been made despite exchanges via the team, the sources said, and prospects for making progress are clouded by the murky outlook of the denuclearization talks between the U.S. and North Korea.