Japan's former prime minister Yukio Hatoyama (L) lays a wreath in front of a memorial stone during his visit to the Seodaemun Prison History Hall in Seoul, South Korea, Aug 12, 2015. [Photo/IC]

A possible explanation is that if the leaders admit the crimes, they would have to compensate, and once the compensation started, it could become endless, Hatoyama said. But "I think it's wrong." he added.

"The issue has been dragging on for 70 years, and I feel deeply sorry for those victims," he added.

Although the Japanese Emperor Akihito did not use words such as "aggression" in a conversation about the war earlier this year, he has said it is necessary to restudy the history of war since the "September 18 Incident", Hatoyama added.