A set of remote islands called Dokdo in Korean and Takeshima in Japanese is seen in this picture taken from a helicopter carrying South Korean President Lee Myung-bak (not pictured), east of Seoul August 10, 2012.
Japan has protested to South Korea against a shooting drill its neighbor plans in disputed waters, Japan's top government spokesman said on Thursday, underscoring tense relations between the two countries.
Relations between Tokyo and Seoul have long been plagued by territorial disputes and resentment that Japan has not properly atoned for its wartime aggression.
The target practice is scheduled to take place on Friday, when Japan plans to unveil the closely-watched results of a review of a landmark 1993 apology to women, many of them Korean, who were forced to work in Japan's military brothels.
Japan was told part of the area designated for South Korea's drill would overlap what it considers to be its territorial waters off a group of contested islets, the Japan Coast Guard said.
The islands, called the Takeshima in Japanese and Dokdo in Korean, are controlled by South Korea, but claimed by Japan as well.
"We cannot accept the practice in light of our country's stance on our territorial right to the Takeshima. It is extremely regrettable," Chief Cabinet Secretary Yoshihide Suga told a regular news conference.
Japan has demanded that the drill be called off, he said.
South Korea's Defence Ministry said its navy planned regular shooting drills on Friday, but declined to comment on the exact location and time of the exercise.
Earlier this year, Japan, mindful of potential diplomatic fallout, said that despite the review, it would not revise the 1993 apology, which recognized the involvement of Japanese authorities in coercing the women to work in the military brothels.