Japan said Wednesday it would soon hold fresh official talks with North Korea after Pyongyang’s surprise promise to investigate the abductions of Japanese nationals.

Chief Cabinet Secretary Yoshihide Suga, the top government spokesman, said the two governments had yet to decide when and where the talks would be held.

On May 29 Tokyo announced it would ease sanctions against North Korea if the secretive state delivers on a pledge to reinvestigate the cases of Japanese citizens snatched in the 1970s and 1980s to train spies.

The announcement, after three days of talks between the two sides in Sweden, marked a major breakthrough in their very strained relationship and was the most positive engagement between Pyongyang and the outside world in many months.

At the time the North agreed to set up a special committee for the investigations which it vowed to launch in about three weeks.

“There is a need for us to make a cautious assessment after closely studying the composition (of the committee),” Suga told a regular news briefing.

North Korea admitted in 2002 that it had kidnapped 13 Japanese citizens to train its spies in Japanese language and customs.

The admission was made when Japan’s then-Prime Minister Junichiro Koizumi travelled to Pyongyang to hold a historic summit with then-North Korean leader Kim Jong-Il.

Five of the abductees returned home but Pyongyang said without producing credible evidence that eight had died, provoking an uproar in Japan.

The subject is highly charged in Japan, where there are suspicions that perhaps even hundreds of others were taken.

Tokyo has suspended talks on establishing diplomatic ties with Pyongyang partly because of what it says is the North’s unwillingness to come clean over the abductions.