Prosecutors next week will drop the case against a Japan Coast Guard navigator who leaked diplomatically sensitive footage of collisions between a Chinese trawler and two JCG cutters near the Senkaku Islands, investigative sources said Thursday.

The Tokyo District Public Prosecutor's Office has determined that the act by Masaharu Isshiki, 44, who received a discharge from the Kobe Coast Guard Office, is "not so intensely illegal and he does not deserve punishment," the sources said.

Isshiki, whose rank was never revealed, was arrested for alleged violations of the National Public Service Law prohibiting civil servants from divulging secrets obtained in the course of his duties. He left the coast guard immediately after police sent the case to prosecutors last month.

Also as a formality, the Naha District Public Prosecutor's Office will not indict Zhan Qixiong, the 41-year-old Chinese trawler captain, who was briefly arrested for ramming his boat into the cutters, after taking worsening Japan-China ties into consideration.

The authorities' monthlong investigation into the run-in, which led to the worst diplomatic row in recent years between Tokyo and Beijing, will thus end.

The prosecutors recognized the leaked footage as "a secret that (Isshiki) could obtain through his duties," but decided against indictment, considering the video was accessible to anyone at the coast guard, and Isshiki confessed to the leakage and the video had already been viewed by Diet members, the sources said.

Isshiki has said he wanted more people to understand the what coast guardsmen face.