TOKYO, Japan (AP) — Japan’s navy went on alert Wednesday after an unidentified submarine made a brief incursion into the country’s southern waters near Okinawa.
Tokyo is trying to determine the origin of the vessel.
The submarine left Japanese waters shortly after it was spotted and a reconnaissance aircraft and destroyer were monitoring its movements, Chief Cabinet Secretary Hiroyuki Hosoda said.
“It’s regrettable,” Prime Minister Junichiro Koizumi told reporters. “It’s certainly not a good thing that a submarine of unknown national origin enters our territorial waters.”
If the submarine’s nationality is identified, Japan will take “necessary steps,” Hosada said, without elaborating.
Japan’s public broadcaster NHK said defense officials were investigating a possible link between the sub sighting and Chinese military vessels detected recently in Japan’s southern waters.
Kyodo News quoted unidentified defense officials as saying that the vessel may be a Chinese nuclear submarine.
A P3C reconnaissance plane confirmed that the submarine had entered Japanese territorial waters near the Sakishima islands in southern Okinawa prefecture, but further details about the vessel had not yet been determined, Hosada said.
Defense chief Yoshinori Ono “issued a maritime alert order,” Hosoda said.
Japan’s Maritime Self-Defense Forces can order the submarine to surface and identify itself, as well as leave Japanese waters, if it tries to re-enter, Hosoda said.
Defense officials confirmed that two Chinese military vessels — a submarine rescue vessel and a towing vessel — were spotted between Friday and Monday in waters 315 kilometers (195 miles) southeast of Japan’s Tanegashima island.
That location is about 1,000 kilometers (620 miles) northeast of the spot where the submarine was found Wednesday morning. Officials, however, refused to comment on a possible link between the two incidents.
Japan has been considering ways to boost its maritime defenses after a shoot out with a suspected North Korean spy ship in December 2001.
In that incident, Japanese Coast Guard patrol boats sank the suspected spy ship in a gunbattle off southwestern Japan. The patrol vessels returned fire only after the ship, ordered to stop, opened fire with a rocket and guns.
The Sakishima islands lie in waters between the northeastern tip of Taiwan and Okinawa’s main island, some 1,600 kilometers (1,000 miles) south of Tokyo.