North Korean leader Kim Jong Un has ordered his aides to "re-explain" to Tokyo the findings of a probe into the whereabouts of missing Japanese nationals suspected to have been abducted by Pyongyang decades ago, according to a South Korean activist.

Kim gave the directive after his historic summit with U.S. President Donald Trump in Singapore last month, said Choi Sung Yong, head of a group representing families of South Koreans abducted by North Korea, citing an informed source in the North's capital.

This would signal a shift in tone from Pyongyang's previous unwillingness to open up dialogue with Tokyo, which has been somewhat sidelined amid the flurry of diplomacy over North Korea's nuclear program, resulting in a recent thaw in relations between the North and the United States.

But skepticism remains over whether North Korea's findings will satisfy Japan.

The investigation in question was carried out by a special committee formed by Kim to revisit the abduction issue in exchange for lifting sanctions, under a May 2014 agreement struck in Stockholm.

But the North disbanded the committee in February 2016 after Japan retaliated over its nuclear and missile tests with fresh sanctions.

(Sakie Yokota visits a photo exhibition of her abducted daughter Megumi in May 2018)

According to Choi's source, the North Korean government says it has already unofficially presented its findings to Japan, but Kim has ordered the probe outcome to be explained again since Prime Minister Shinzo Abe's administration claims to have never been briefed about it.

Japan claims that 17 of its citizens were abducted in the late 1970s and early 1980s, five of whom were repatriated in 2002, and also suspects the North was involved in many more disappearances.

North Korea has said eight of the 17 -- including Megumi Yokota, who disappeared while heading home from school when she was 13 -- have already died, while four never entered the country, an account Japan has dismissed as unreliable.

The source said that Kim did not see any need to hold dialogue with Japan before his summit with South Korean President Moon Jae In in April, instead favoring relations with the United States, China and Russia.

But Kim apparently changed his mind after both Moon and Trump brought up the abduction issue in their respective talks, opting to see whether Japan would accept its probe findings.

(Shinzo Abe, left, then Japan's deputy chief Cabinet secretary, shakes hands with North Korean leader Kim Jong Il during Prime Minister Junichiro Koizumi's historic trip to Pyongyang in September 2002)