The Japanese Prime Minister, Junichiro Koizumi, has told the relatives of 13 Japanese citizens kidnapped by North Korea that the issue remains his top priority in dealings with Pyongyang.

The Japanese leader met the family members before a government team left on Friday for the North Korean capital, where it will investigate the kidnappings.

Koizumi pledged to consider the families' feelings

North Korea admitted to and apologised for the abductions, which took place in the 1970s and 80s, at an historic summit with Mr Koizumi last week.

Pyongyang says only five of those kidnapped are still alive, but the relatives told Mr Koizumi they wanted to see proof of the deaths and also demanded the rapid return of the survivors.

The relations of those confirmed still alive have refused a government proposal that they visit the kidnapped in North Korea, insisting that they should instead by returned to Japan within a month. Pyongyang says they are free to leave.

Test material

Tokyo says it wants to use DNA testing to check whether both the surviving and deceased kidnapped are who Pyongyang says they are, and to investigate how they died.

Shigeru Yokota, whose daughter was abducted when she was 13, gave the government team a clipping of her hair. Other families provided old photographs and letters.

The relatives are infuriated by Japan's failure to confirm any of the details provided by North Korea and the government's decision to now forge diplomatic relations with North Korea.

Mr Koizumi promised during the hour-long meeting to "respect the families' feelings when we discuss formalising ties".

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But Mr Yokota told a press conference afterwards that he was disappointed.

"We had hoped that the prime minister would give us a more clear-cut explanation about how he plans to address our demands," he said.

Hatsui Hasuike, whose son disappeared after meeting his girlfriend in a library in 1978, said: "We want the prime minister to reply to our 25 years of suffering."

The North Korean official news agency warned Japan on Friday not to get carried away by emotion over the kidnappings, saying they would never compare to atrocities carried out by the Japanese army before and during World War II.

"Arguing over the two issues, standing in confrontation, carried away by emotion, would entail unpredictable consequences," KCNA warned.

The BBC's correspondent in Tokyo, Charles Scanlon, says it is the first indication that North Korea may be losing patience with the furore over the abductions.