Japan's PM Junichiro Koizumi has said he is not satisfied with North Korea's explanations about Japanese citizens it abducted in the 1970s and 1980s.
North Korea says kidnap victim Megumi Yokota committed suicide
Mr Koizumi was speaking after Japanese officials ended talks in Pyongyang on abductees the North says are now dead.
North Korea handed over documents and the remains of Megumi Yokota, one of the missing, Japanese media reported.
North Korea admitted to some abductions two years ago, but suspicions remain about others Pyongyang says have died.
Mr Koizumi told reporters that Japan needed to continue talks with North Korea to learn more.
Snatched in the '70s and '80s
Used as cultural trainers for N Korean spies
Five allowed home in 2002
Five children now freed from N Korea
Eight said to be dead, others missing
''I can see signs of effort on the part of the North Koreans, but there are points in which the contents are not something Japan can be satisfied with,'' Mr Koizumi said, Kyodo news agency reported.
Mr Koizumi also said he remained cautious about imposing economic sanctions on North Korea.
He was speaking after a Japanese delegation returned to Tokyo from Pyongyang with documents and personal belongings of those thought to have been abducted.
"Various materials have been presented and I have been told it is important to bring them back while preserving them in their present state," Chief Cabinet Secretary Hiroyuki Hosoda told reporters.
The delegation was also reported to have returned with the remains of Megumi Yokota, who was kidnapped from Japan by North Korean spies in 1977 when she was just 13.
When North Korea admitted in 2002 that its agents had abducted several Japanese nationals, it said that Ms Yokota had killed herself in a hospital in 1993 while being treated for depression.
North Korea admits to having kidnapped 13 people in all, who were used to train Korean spies. Five have returned to Japan, and Pyongyang says the rest have died.
But Tokyo is sceptical about inconsistencies in North Korea's accounts, and wants proof the others are dead. It also wants information on another two people whom North Korea says never entered the country.
Senior members of Japan's ruling party had called for economic sanctions on North Korea if this round of talks, which began on Wednesday, were unfruitful.
Japanese Foreign Minister Nobutaka Machimura said on Sunday that North Korea seemed to be becoming more open about the abduction issue, but that Tokyo still had not ruled out the possibility of sanctions.