By Chris Hogg
BBC News, Tokyo
Japan has asked North Korea to hand over a man they believe helped to abduct a Japanese man 26 years ago.
Mr Sin is already on an Interpol wanted list
Sing Guang-su, 76, is already wanted by Tokyo for his alleged part in the kidnap of four other Japanese citizens.
Japan made the request through diplomatic channels in Beijing as Japan and North Korea do not have diplomatic relations.
Four years ago North Korea admitted its agents had kidnapped 13 Japanese citizens in the 1970s and 80s.
They used the captives to train their spies, to teach them about Japanese language and culture. Five were later returned. Pyongyang said eight others had died.
Many in Japan suspect some may still be alive though.
One of those said to have died, Tadaaki Hara, was kidnapped in 1980. He was 43 at the time.
Police investigations suggest he was tricked by two men who said they had a job offer for him. It is thought he was kidnapped and taken to North Korea by boat.
On Monday arrest warrants were issued for the two men accused of carrying out the abduction. One is an elderly North Korean now living on a South Korean island.
The other, Sing Guang-su, who is also in his 70s, is believed to be in North Korea.
Mr Sing is already on an Interpol wanted list. He is alleged to have kidnapped four other Japanese citizens.
So this latest move is largely symbolic. Posting additional charges relating to the abduction of Mr Hara appears to be part of Japan's efforts to step up the pressure on North Korea.
Various attempts to resolve the abduction issue via talks have so far yielded little progress.