Officials in Japan are investigating a cyberattack on defense contractor Mitsubishi Heavy Industries that occurred in August, but was only learned of in the past week.

Defense Minister Yasuo Ichikawa said he is not aware that any sensitive information was compromised. But he told reporters in Tokyo that Mitsubishi has been ordered to review its computer security systems, and that authorities will continue to monitor the situation.

Mitsubishi makes fighter jets, missile defense systems, submarines and other military equipment. Japanese defense officials say they found out about the cyberattack through press reports, and that Mitsubishi should have informed them of the breach.

Another Japanese defense contractor, IHI, says it also came under cyber attack. The company says it has received an increasing number of e-mails carrying virus-ladden attachments.

Computer security analysts say there have been similar attacks against companies in the United States and India over the past year.