Japan plans to extend its sanctions against the Democratic People's Republic of Korea for two more years when they expire on April 13, after failing to get promised updates on an investigation into the kidnapping of Japanese citizens decades ago, the government spokesman said on Tuesday.

"At this point, we are asking North Korea to ensure it quickly conducts the investigation into the abductions and other areas and make sure they report to us," Chief Cabinet Secretary Yoshihide Suga told reporters. "The results need to be shared quickly and informatively."

Suga said Japan had decided that keeping the sanctions in place would be the "most effective approach" in handling the situation.

Japan bans DPRK-registered ships from entering its ports except for humanitarian reasons. It also bans chartered flights between the countries.

In 2002, the DPRK admitted to kidnapping 13 Japanese in the 1970s and 1980s to train spies in Japanese language and culture. Five of them were allowed to return to Japan the same year, and Pyongyang says the others had died or never entered the country.

Japan believes hundreds more may have been abducted and that many of them may still be alive, and questions over their fate, along with other issues such as the DPRK's nuclear program, have kept relations frozen.

Prime Minister Shinzo Abe has made securing some progress on the issue a high priority for his administration, and in the biggest step forward in years, the DPRK agreed in May of last year, during talks in Stockholm, to reinvestigate the abductions. It also promised an inquiry into all Japanese nationals living in the DPRK.

In exchange, Tokyo lifted a ban on the DPRK's visiting Japan, allowing them in on a case-by-case basis, and made it easier for Japanese and ethnic Koreans in Japan to travel to the DPRK.

It also raised the limit on money taken or sent to the DPRK and approved port calls by the DPRK ships, but only for humanitarian purposes, limited to small shipments of food, medicine and clothes.

Japan still abides by separate UN sanctions imposed because of the DPRK's nuclear and missile programs. They include an arms trade ban, a freeze of its assets, a ban on people exchanges and restrictions on education and training.

Xinhua contributed to this story.

(China Daily 04/01/2015 page11)