Japan's prime minister is turning up the pressure on North Korea to answer questions over the fate of possibly hundreds of Japanese citizens believed to have been abducted by the North's agents in the 1970s and 1980s.

Shinzo Abe told a rally in Tokyo on Saturday that he will not back down until every abductee is accounted for. Suggesting he believes some are still alive, he said he will not relent until they are allowed to come back to Japan.

Abe's remarks came as North Korea is preparing to announce the results of a new investigation into the matter following an agreement in May.

Japan recognizes 17 cases, but an independent investigative commission and police suggest the number could be as high as 869.