The United Nations special envoy on North Korea says harsh human rights conditions in the country have hardly changed and that criminal responsibility should be pursued against leader Kim Jong Un.

Marzuki Darusman said Friday in Tokyo that little has changed during his six years as special rapporteur and his repeated requests to visit North Korea have never gone through.

He said it is "imperative" for the international community to seek criminal responsibility and to apply political pressure to improve human rights in the country.

Darusman is in Japan to assess North Korean human rights development and he has talked to Japanese police and legal experts, as well as relatives of Japanese citizens abducted to North Korea decades ago.