国こく籍せき不ふ明めい

noun which may take the genitive case particle 'no'

of unknown nationality; unidentified

Used especially for vessels, aircraft, or other entities whose nationality cannot be determined. Often appears in news or official contexts.

• 国こく籍せき不ふ明めいの船ふねが領りょう海かいに侵しん入にゅうした。

  A ship of unknown nationality entered territorial waters.

• 国こく籍せき不ふ明めい機きが防ぼう空くう識しき別べつ圏けんに接せっ近きんした。

  An unidentified aircraft approached the air defense identification zone.