An adviser to Japan's Cabinet has arrived in North Korea amid a slight easing of tension on the Korean Peninsula after weeks of threats from the North aimed at Washington, Seoul and Tokyo.

The purpose of the trip Tuesday by Isao Iijima wasn't immediately known. Tokyo's Foreign Ministry said it has no information about Iijima's whereabouts and the prime minister's office refused to comment.

Iijima was a senior aide to former Japanese Prime Minister Junichiro Koizumi, who met with late North Korean leader Kim Jong Il in 2002 and 2004.

Japan is a participant in now-dormant six-nation talks aimed at ending North Korea's nuclear weapons program.

Japan and North Korea are also at loggerheads over Tokyo's demand for information about Japanese citizens who were kidnapped by the North decades ago.