South Korea lodged a formal protest on Friday shortly after Japan approved an annual foreign policy report that renewed a territorial claim to Seoul's easternmost islets of Dokdo.

Escalating diplomatic tensions with South Korea, Japan formally issued the Diplomatic Blue Book 2013 that reiterated its claims that Dokdo is Japanese territory historically and under international law.

"The Korean government strongly protests against the Japanese government's endorsement of the Diplomatic Blue Book that contains an unjust sovereignty claim to Dokdo," foreign ministry spokesman Cho Tai-young said in a statement.

"(South Korea) once again emphasizes that, in order for the two countries to restore the trust between them, the Japanese government should heal the wounds of the past as soon as possible by looking squarely at its past and acting in a responsible manner," Cho said, demanding Japan "immediately withdraw" the claim to Dokdo.

The ministry summoned Takashi Kurai, Japan's deputy chief of mission in Seoul, and delivered a letter of protest demanding Japan immediately retract its claim to Dokdo, officials said.

Dokdo, a group of rocky outcroppings lying in the East Sea between the two countries, has been a source of diplomatic tension between the two countries for years.

Japan has long laid claims to Dokdo in the country's school textbooks, government reports and through other avenues, stoking enmity in South Korea against its former colonial ruler. South Korea views the claims as a sign that Japan has not fully repented for its imperialist past.

South Korea also says the territorial claims amount to Japan denying Korea's independence from its 1910-45 colonial rule, because Korea had reclaimed sovereignty over its territory -- including Dokdo and many other islands around the Korean Peninsula -- when it regained independence.

South Korea has kept a small police detachment on Dokdo since 1954.

The Friday approval of the annual diplomatic paper is likely to dash hopes of improving ties between the new governments in South Korea and Japan. Relations sank to one of the lowest-ever ebbs after Park's predecessor, former President Lee Myung-bak, made an unprecedented visit to Dokdo last year. (Yonhap News)