Korea on Tuesday protested Japan’s repeated sovereignty claims to the easternmost Dokdo Islets in its annual defense white paper, further straining relations between the neighboring countries.

Earlier in the day, Tokyo claimed the islets in the East Sea along with the South Kuril Islands --- referred to as “northern territories” by Japan -- as its “own territory.” The annual document also said that the disputes involving the cited lands remain unsettled.

It marks the 12th straight year that Japan has rehashed such claims. As in the year before, the paper also carried a map of the country’s air defense identification zone, outcropping skies over the Dokdo Islets as its territorial airspace and denoting the Dokdo Islets by its Japanese name “Takeshima.”

“The (Korean) government strongly condemns the Japanese government including its sovereignty claims to Dokdo Islets, which is clearly our own territory by historical, geological and international standards, in the 2016 defense white paper on Aug. 2,” Foreign Ministry spokesman Cho June-hyuck said in a statement, urging Tokyo to cease what the ministry called its “futile claims” to the Dokdo Islets.

The ministry called in Kohei Maruyama, a minister of the Japanese Embassy in Seoul to lodge a formal protest.

Seoul’s Defense Ministry also summoned a defense attache at the Japanese Embassy earlier in the day, and delivered a statement of complaint.

“Korea’s Ministry of National Defense will firmly react against any attempts to infringe upon the sovereignty of the Dokdo Islets, and will seamlessly protect our rights to the Dokdo Islets,” the statement said.

Located in waters between Korea and Japan, the Dokdo Islets lie in ample fishing grounds and is believed to hold rich reserves of natural gas and other resources.

Prior to annexation of Korea, Japan illegally incorporated the islets in 1905 as part of its territory. Seoul regained control of it in 1945 upon its independence but Tokyo has repeatedly attempted to claim the islets and the surrounding waters -- which they call the “Sea of Japan” -- as its own.

Japan’s renewed claims on the Dokdo Islets dealt another blow to the tumultuous relations between the two countries, which has been marked by recent territorial and historical disputes stemming back to Japan’s 1910-1945 colonialization of Korea.

The icy relations had shown signs of thawing, with the two governments agreeing in December on a landmark deal on Japan’s enslavement of Korean women during World War II, euphemistically called “comfort women.” The agreement centered on launching a 1 billion yen ($9.77 million) foundation on helping the victims of sexual slavery.

But the agreement was marred by the conservative Shinzo Abe administration’s remarks denying the coerced nature of the comfort women and insistence that Seoul remove a statue of a girl -- a symbol of the comfort women -- that stands adjacent to the Japanese Embassy in Seoul.

In addition to the Dokdo Islets claims, Tokyo’s annual document addressed North Korea’s nuclear threats, saying that there is a possibility that the communist nation has achieved miniaturization of the nuclear warheads. Making the warheads small enough to fit ballistic missiles is considered a critical step in achieving nuclear strike capacity.

Pyongyang has been upping efforts in its nuclear and ballistic missile programs on orders from its leader Kim Jong-un.

It also raised concern over the territorial dispute in the South China Sea and accompanying military tension between China and the U.S. The document accused China of attempting to carry out its unilateral claims through force.

By Yoon Min-sik  (minsikyoon@heraldcorp.com)