Senior Japanese and North Korean diplomats were due to resume rare "tough" talks on Friday, with Tokyo expected to press Pyongyang on its kidnapping of Japanese nationals and its arms programme.

Japanese negotiator Shinsuke Sugiyama said the two sides held "serious" talks on Thursday in the Mongolian capital.

"Although the consultation itself is not an easy matter, both sides have exchanged views sincerely," Sugiyama told Japanese reporters Thursday night, after a nearly seven-hour session.

"The atmosphere of the meeting was not acerbic. It was direct, serious and very rich in substance. We discussed a wide range of subjects in depth," Sugiyama said.

The direct talks between Sugiyama and his North Korean counterpart Song Il-Ho were the first senior, working-level meeting between the two nations in four years.

The countries do not have diplomatic ties and have long been at odds, with Tokyo pressing Pyongyang to come clean over past abductions of Japanese nationals and its nuclear ambitions.

In 2002 Pyongyang admitted its agents had kidnapped Japanese nationals in the 1970s and 1980s to train its spies in Japanese language and customs.

For its part, North Korea maintains Japan has not made up for its war-time aggression. It demands compensation and atonement.

One of the key points for Friday's meeting will be whether the North will keep the door open and allow the two sides to continue exchanges, Japanese media said.

The talks became possible after an earlier exchange between mid-level Japanese and North Korean diplomats in August in Beijing.

Mongolian President Elbegdorj Tsakhia told AFP in Ulan Bator he was delighted the two nations had come together in his country.

"You know Japan, North Korea and other countries can come to discuss this issue on Mongolian soil. We would like to contribute to that. That is our only purpose. We are happy to host this kind of meeting in Ulan Bator," he said.

However, media in Japan said little substantive progress is expected because of the looming general election at home.

Prime Minister Yoshihiko Noda's ruling Democratic Party of Japan is widely expected to be booted out of office in polls on December 16.