The Defense Agency has conducted an internal probe into what it says are media leaks that resulted in two newspaper reports detailing Chinese military operations last May and September, informed sources have said.
The probe was conducted by a police unit that handles criminal investigations for the Self-Defense Forces, the sources said.
The investigation was prompted by a series of rare complaints about leaks from the agency's intelligence division, the sources said. Leaking defense secrets is a violation of the SDF law.
The complaints -- filed between fall and earlier this year -- named no suspects and no media organizations, the sources said.
An intelligence division official said the entity "cannot comment on whether (such) a complaint has been filed."
A media law expert suggested that attempts to criminalize an informant within the defense apparatus may generate controversy by threatening citizens' right to know and limiting the freedom of the press.
The probe apparently concerns a May 2005 media report on a Chinese submarine that went inoperative after an accident in the South China Sea, and a September 2005 report on a plan by the Ground Self-Defense Force that envisages China attacking Japan -- something the nation's top leaders and defense papers have been alluding to for some time -- the sources said.
One reason the agency is apparently rushing to clamp down on information leaks is because the report on the Chinese submarine accident contained satellite data from the United States military, the sources said.
The United States, Japan's most important ally, has been repeatedly pressuring Tokyo to step up controls on secret information since the two countries began increasing the volume of military information they share in the 1990s.
Under the SDF law, officers face a year in prison with hard labor for leaking confidential information on their duties.
An October 2001 amendment to the law increased the penalty to up to five years of prison with hard labor.