Japan repeated its territorial claim Tuesday over Dokdo, a pair of outcroppings in the East Sea, in its annual foreign policy report, dealing yet another blow to the already-troubled ties with South Korea.
 

In the 2015 Diplomatic Bluebook, the Shinzo Abe administration argued that Dokdo, effectively controlled by Seoul, is Japanese territory based on historical facts and international law.
  

It came a day after Japan's education ministry irked South Koreans by unveiling the results of its regular review of textbooks for middle school students.
  

In 2011, only 4 out of 18 total textbooks contained Tokyo's claim that South Korea is illegally occupying Dokdo, where a small dispatch of Seoul's police are stationed as a token of its ownership.
  

This year, the number jumped to 13, representing the Shinzo Abe administration's attempt to bolster its efforts to lay claim to Dokdo.
  

Japan's move, which South Korean officials describe as a provocation, apparently undermined efforts to improve relations between the neighboring nations. Seoul-Tokyo ties have long been strained despite brisk economic and cultural exchanges due to long-standing stand-offs over territory and shared history.
  

It's a legacy of Japan's brutal colonial rule of Korea from 1910-45. South Koreans believe Japan has never offered a sincere apology for its wartime atrocities.
  

Continued disputes between Seoul and Tokyo are a major stumbling block to Washington's push for closer trilateral cooperation in regional security amid growing military threats from Pyongyang. (Yonhap)