Prime Minister Junichiro Koizumi said Monday he has ordered a review of the response Saturday to a possible spy ship in Japan's exclusive economic zone with a view to enhancing the country's ability to deal with similar cases in the future.

"(The foreign ship) had made considerable preparations and armed itself for an attack, so the Japanese side must also think of ways to deal with such incidents while keeping in mind that such reckless unidentified ships exist," Koizumi said. "There is a possibility that a similar incident will take place in the future, so we should review the legal aspect as well as taking a realistic approach to see what needs to be done."

Koizumi said that although he thinks the Japan Coast Guard responded well, there are still areas that need attention, such as its cooperation with the Self-Defense Forces, which was criticized in Monday's meeting for not being close enough at hand during the incident.

"I think there are various issues that need to be reviewed, such as the (coast guard's) coordination with the Defense Agency, its equipment, the warning shots that were fired and the safety" of its personnel, he said.

Following Koizumi's remarks, the government began studying the advisability of revising certain laws to ease regulations on the use of firearms by coast guard personnel, in case similar incidents occur outside Japan's exclusive economic zone.

The government hopes to pass bills required to amend the SDF Law and the Maritime Safety Agency Law during the next regular Diet session, which is expected to convene in late January, government sources said.

An unidentified ship sank in the East China Sea on Saturday night after an exchange of fire with Japanese patrol boats. The bodies of two of about 15 crew members on the ship were recovered. The government is becoming increasingly certain that the ship was North Korean.

Koizumi is considering taking legal steps to ensure the safety of coast guard personnel, Chief Cabinet Secretary Yasuo Fukuda said.

"We are not allowed to do anything until someone suffers injuries," Fukuda said. "The question of whether this arrangement ensures the safety of coast guard personnel, this is important. We should think about what to do beforehand (to prepare) for when we face opponents who are truly dangerous."

Fukuda said there would be no need to recover the ship if investigations can be carried out in another form, such as by using divers.

Defense Agency chief Gen Nakatani said the government should consider making legal changes to empower it to take "swift and strong" measures to stop unidentified ships.

Nakatani also said his agency is boosting patrols around Japan in the wake of the incident.

Foreign Minister Makiko Tanaka said Japan will prepare for any developments, including possible retaliatory measures.