Japanese coast guard officials say North Korea has banned ships from
sailing off its east coast for 16 days starting this Thursday.
Coast guard officials say the North Korean government sent them an e-mail warning that it will hold military drills off its eastern port of Wonsan between Thursday and July 10.
The e-mail did not say what consequences ships would face if they violated the ban.
The dates fall within a time frame mentioned last week by Japanese media for a possible launch of a long-range missile toward Hawaii. The message comes at a time of heightened tension between Pyongyang and the international community.
A U.S. Navy destroyer, the USS John S. McCain, is tracking a North Korean ship suspected of smuggling missiles or related parts in violation of United Nations sanctions.
China warned Tuesday that nations tracking North Korean ships should have ample evidence and proper cause before seeking to check the cargo of ships.
Speaking a regular press conference Tuesday China's Foreign Ministry spokesman said that under the current circumstances, all parties should refrain from taking actions that could escalate the situation.
Reports citing unidentified intelligence sources in South Korea say the vessel, the Kang Nam, appears to be heading to Burma by way of Singapore.
The ship is the first to be monitored under a new U.N. Security Council resolution.
The resolution, which was adopted earlier this month, authorizes U.N. members to inspect North Korean cargo ships for illicit missile-related technology. North Korea has said it would consider such inspections an act of war.
The U.S. military has not indicated any plans to search the vessel, which belongs to a fleet that U.S. officials say has been used in the past to transport weapons.
Some information for this report was provided by AP and Reuters.