TOKYO - Japan on Tuesday approved a two-year extension of its unilateral sanctions imposed against the Democratic People's Republic of Korea (DPRK), a local report said.

The decision showed that Japan sees no tangible progress in the DPRK's investigation into the abduction of Japanese nationals in the 1970s and 1980s, said Japan's Kyodo News.

The sanctions, which will be expired on April 13, included a ban on the entry into Japanese ports of DPRK-registered ships except for humanitarian purposes, and on chartered flights between the two countries.

Japan partially lifted its sanctions last July as the DPRK launched a new round of investigations into the whereabouts of the Japanese abductees.

The abduction issue prevents the two countries from forming diplomatic ties.