Japan has protested to the United States after a U.S. nuclear submarine made an unannounced visit to one of its ports Monday.
A statement from the Japanese Foreign Ministry says Tokyo reminded the United States that it must give Japan at least 24 hours notice before submarines arrive at its ports.
Japan has asked U.S. officials to explain why the USS Providence arrived on the southern island of Okinawa today without prior notice. The U.S. embassy in Japan said the incident was due to what it called "miscommunication" in the U.S. Navy.
Nuclear-powered vessels are a touchy topic in Japan, the only country to have been attacked with atomic bombs.
The unannounced visit comes just two days after an accident on a Russian nuclear-powered submarine in the Sea of Japan killed at least 20 people.
The recent arrival of a nuclear-powered U.S. aircraft carrier in Japan triggered protests after it made a port south of Tokyo its new home.
Some information for this report was provided by AFP, AP and Reuters.