Information related to communication networks involving the Self-Defense Forces may have leaked after cyberattacks earlier this month against NTT Communications Corp., a source familiar with the case has said.

The Defense Ministry is investigating in cooperation with the company, an affiliate of Nippon Telegraph and Telecom Corp., suspecting that the possible leaks could affect operations of the SDF's core system, the source said Thursday.

The suspected leaks involve information about communications equipment and layout of a Maritime Self-Defense Force facility in Yokosuka, Kanagawa Prefecture, as well as that of communication lines in about 10 SDF locations.