An adviser to Japanese Prime Minister Shinzo Abe left Pyongyang by air on Friday, completing a four-day visit to North Korea, the North's official Korean Central News Agency reported.
Isao Iijima is believed to be heading to Beijing before returning to Tokyo possibly on Saturday, according to informed sources.
In Tokyo, Chief Cabinet Secretary Yoshihide Suga said earlier Friday that the Japanese government will receive a briefing by Iijima about the unannounced trip after he returns home.
Iijima held talks Thursday in Pyongyang with Kim Yong Nam, president of the Presidium of the Supreme People's Assembly, North Korea's parliament, and the two sides are believed to have discussed steps to improve bilateral relations, including how to resolve the issue of North Korea's abduction of Japanese nationals in the 1970s and 1980s.
"The abductions are the most important issue for the (Japanese) administration. Prime Minister Abe has a strong desire to solve the issue, feeling it is his responsibility," Suga said at a news conference.
Along with No. 2 leader Kim, Iijima met with Kim Yong Il, a secretary of the Central Committee of the ruling Workers' Party of Korea who doubles as director of the party's International Department, and Song Il Ho, ambassador for talks to normalize relations with Japan.
The visit, which came amid North Korea's increasing isolation in the international community over its nuclear and missile ambitions, surprised the United States and South Korea, which have been working closely with Japan on coordinating North Korea policy.
In an apparent attempt by North Korea to publicize what may be seen as improved ties with Japan, KCNA's website carries video footage showing a handshake between Iijima and Kim Yong Nam and a photo session between the two men.
Japan and North Korea, which do not have diplomatic relations, resumed intergovernmental negotiations in August last year after a four-year hiatus.
But the talks were suspended in the wake of the North's launch of a long-range rocket in December that other countries believe was actually a covert test of ballistic missile technology in violation of U.N. Security Council resolutions.
On Friday, senior Japanese officials tried to allay concern that Iijima's trip may have undermined trust in trilateral policy coordination on Pyongyang.
"Cooperation among Japan, the United States and South Korea is very important," Foreign Minister Fumio Kishida told journalists. "We must try to communicate with each other sufficiently."
"It is important (Japan) does not cause any concern to both the United States and South Korea," Yoshihisa Inoue, secretary general of the New Komeito party, a junior coalition partner of Abe's Liberal Democratic Party, said at a press conference.
Inoue said issues surrounding North Korea must be solved at the six-nation talks on ending Pyongyang's nuclear ambitions, which also involve China and Russia and have been stalled since 2008.
The Japanese government recognizes 17 nationals, including five who were repatriated to Japan in October 2002, as having been abducted by North Korea in the 1970s and 1980s. The issue remains a key obstacle to normalizing relations between the two countries.