Japanese maritime officials say North Korea has restricted passage in a designated area off its northeastern coast.

The Japan Coast Guard said Friday that it had intercepted a warning by North Korean authorities for ships to stay away from waters in a 130-kilometer coastal range near Kimchaek, North Hamgyeong Province.

North Korea issued the warning to be effective until May 30th, from ten am to six pm daily. However, it did not give reasons for the warning.

A Japanese official said North Korea may be preparing to fire a short-range missile, but it will not pose a direct threat to Japan.