Oct. 1 (UPI) -- South Korea defended a decision to fly F-15K fighter jets over disputed islets in the East Sea following strong protests from Japan.
As part of a commemoration marking the founding of the military, Seoul's fighter jets had conducted a patrol over Dokdo, also known as Takeshima in Japan, South Korean news service News 1 reported Tuesday.
Japanese foreign ministry official Shigeki Takizaki called the South Korean embassy to express "deep regret," according to Japanese press reports.
Japan and South Korea each claim the islets as part of their territory. On Monday Takizaki reportedly said "Takeshima, as clearly reflected in history, is Japanese territory, even under international law."
Japan did incorporate Dokdo into its territory when it annexed the Korean Peninsula in 1905. Japan's claims are no longer valid following the end of World War II and colonial occupation, according to Seoul.
The Japanese diplomat also said South Korea flights are "unacceptable."
Taro Kono, Japan's new defense minister, said the flights would interfere with security cooperation between South Korea and Japan.
"I hope [South Korea] responds wisely," Kono said.
South Korea rejected Japan's claims to Dokdo. Seoul's military said Dokdo is "clearly the territory of the Republic of Korea" and protested Japanese statements.
South Korea flew four jets in observance of the 71st anniversary of the country's Armed Forces Day, over Dokdo and also the island of Marado. It patrolled other areas of the peninsula, including areas of the West Sea or Yellow Sea, according to News 1.
South Korea's relations with Japan remain strained at a time when Tokyo is cooperating with other partners on monitoring North Korea.
Japan's foreign ministry said Tuesday Canada and Japan have been cooperating in the surveillance of North Korean vessels engaging in illicit ship-to-ship transfers at sea, Yonhap reported.
Tokyo also said Canadian forces will be allowed to be stationed at Kadena Air Base in Okinawa, for the purpose of transshipment monitoring.
Kadena is a U.S. air force installation.