North Korea may have frequently abducted citizens from other countries under its former leader, Kim Jong-il, according to the Guardian, which cited a report by a Japanese newspaper. The newspaper, the Tokyo Shimbun, said it has obtained secret documents that instructed spies how to carry out kidnappings in foreign countries without being captured.

Some have questioned the document’s authenticity because they say the Korean word for “abduction” is written in a South Korean style rather than one used in the totalitarian nation. However, the newspaper said this was done intentionally to help North Korea’s spies assimilate, as they primarily targeted South Koreans for abduction.

If accurate, these reports would bolster claims by Japan that North Korea had a network of agents who were trained to capture citizens in Japan and other countries. Japan has said these kidnappings were part of a program and not done by rogue agents, according to the Guardian. The country claims North Korea took 17 of its citizens in the 1970s and 1980s with the goal of teaching North Korean spies the Japanese language and culture so they could move undetected while on missions.

The 356-page manual was used at the Kim Jong-il Political-Military University, the Japanese newspaper reported. One portion of the document explains the logistics of kidnapping people in other countries.

“To abduct the target, one has to know the target’s address, where the target enters and exits, day-to-day traffic routes, means of transportation and their timeline as well,” it said, according to NK News.

The Japanese government is still seeking information about at least 12 people it believes were taken by North Korea. This summer, Japan Times reported that the country’s Prime Minister Shinzo Abe asked the United States to help rescue Japanese citizens abducted by North Korea in the event of a crisis in the region.

In 2002, Japan secured the release of five abductees after a summit with Kim Jong-il, according to the Guardian. The country refuses to believe North Korean claims that eight of the last 12 captives have died, and the other four never entered North Korea.

These new documents reported by the Tokyo Shimbun would be the first physical evidence of these kidnappings. However, it is unclear if the evidence will help Japan in its negotiations with North Korea because the documents were written at least 15 years ago.

“But the families of the abductees and their supporters can now point to this document as proof that North Korea systematically organized the abductions,” the Tokyo Shimbun reporter told the Guardian. “That will enable them to put pressure on the Japanese government to do more to settle the matter.”