Japan engaged in several informal contacts with North Korea this spring, sources close to the matter have said, apparently to seek a breakthrough in a long-standing impasse surrounding the abduction of Japanese nationals in the past.

Prime Minister Fumio Kishida has aimed for a summit with North Korean leader Kim Jong Un, but apparently no progress has been made, the sources said Friday. The two nations have no diplomatic ties.

Regarding media reports that Japanese officials contacted the North Korean side in March and May, Kishida told reporters Friday that he would "refrain from making comments due to the nature of the matter."