Dec. 13 (Bloomberg) -- Japanese police arrested a navy officer on suspicion of leaking classified data on the Aegis combat system used on battleships, a statement said.

Police and naval investigators in Kanagawa prefecture near Tokyo took Sumitaka Matsuuchi, a 34-year-old lieutenant commander, into custody today for his suspected role in the leak, the police statement said.

The leak was discovered earlier this year when information on the capabilities of the Aegis was found on the home computer of a second-class petty officer in Kanagawa in January. Defense Secretary Robert Gates in May told Japan's defense minister at the time, Fumio Kyuma, information security is crucial to cooperation on missile defenses.

``The investigation that started in January is reaching its final phases,'' Chief Cabinet Secretary Nobutaka Machimura said today at a press conference. ``This is evidence that not only the defense ministry but the whole Japanese government hasn't taken intelligence issues seriously enough.''

Matsuuchi is suspected of passing Aegis system data stored in a compact disc to an instructor at a naval training school in Hiroshima prefecture west of Tokyo around August 2002, the police statement said.

He's being detained on suspicion of violating an intelligence protection law related to Japan-U.S. defense agreements.

The Aegis is an advanced weapons system which can detect, track and provide guidance to missiles for multiple targets simultaneously, according to the U.S. Navy Web site.

Japan and the U.S. signed an agreement to boost protection of military intelligence in August, following the leak.

To contact the reporter on this story: Sachiko Sakamaki in Tokyo at ssakamaki1@bloomberg.net.

Last Updated: December 13, 2007 01:39 EST