North Korea fired a ballistic missile over the Japanese islands in 1998 and relations between the two countries have remained testy.

"It would be useful to be prepared to carry out a campaign for intercepting the missile in flight and use force against the missile base, in a simultaneous and parallel action, when the opposite side sets out to launch a missile attack on Japan," the National Institute for Defense Studies said.

The report, scheduled to be published on Friday, said it would be important to have extensive discussion at "political level" on the "significance and limit" of such striking power.

The think-tank, affiliated to the Defense Agency, briefed foreign media on Thursday on the report, entitled "East Asian Strategy Review."

Japan's Defence Agency director Shigeru Ishiba has said in parliament last year that, if North Korea were about to launch a missile at Japan, it would not be unconstitutional to make a preventive attack on the launch site.

Ishiba has said such pre-emptive strike abilities have been entrusted so far to the US forces under a security pact.

Japan's post-war constitution bans the use of force in settling international disputes and its military, called the Self-Defense Forces, has been limited to a purely defensive chore.

Japan has been conducting joint research with the US on developing a sophisticated missile defence system since 1999, a year after North Korea's firing of the missile over Japan and into the Pacific.

The report said that North Korea is deploying "175-200" Rodong missiles with a range of about 1,300 kilometers (800 miles) at present and seen capable of "striking almost all parts of Japanese territory."

"Japan has become more vulnerable as it is subject to a situation in which Tokyo, like Seoul, can be taken hostage by North Korea in military terms, as a result of the deployment of the Rodong missiles and due to the lack of preparations on the part of both Japan and the United States to counter the move with effective means," the report said.

WAR.WIRE