Seoul will respond strongly to Tokyo's latest claim to the South Korean islets of Dokdo included in Japan's annual defense document, officials said Tuesday, in an indication of the country's growing intolerance for Japan's territorial claims.

Japan approved its 2011 defense white paper earlier in the day, using the same language since 2005 to refer to Dokdo as Japanese territory. The East Sea islets have been an ongoing source of tension between the neighbors as South Korea flatly dismisses any attempt by Japan to lay claim to the set of rocky outcroppings.

The move comes one day after three Japanese lawmakers of the conservative Liberal Democratic Party were forced to return home after being denied entry at a Seoul airport over their plan to visit Ulleung Island, located 90 kilometers west of Dokdo. The trip was seen as an attempt to bolster Japan's claims to South Korea's easternmost territory, and Seoul justified its response based on its immigration laws, which allow an entry ban for people who could harm the country's interests or the public's safety.

The foreign ministry said it has summoned Nobukatsu Kanehara, a diplomatic minister at the Japanese embassy here, to express regret over the defense paper's claims to Dokdo. In previous years, the ministry has summoned the Japanese embassy's councilor with lower rank than a minister.

The ministry's spokesman also plans to issue a statement later in the day to protest Tokyo's latest move, instead of a lower-ranking ministry official who has been in charge of it in the past.

The defense ministry here also expressed its "deep regrets" over Tokyo's latest claim to Dokdo. In a statement, the ministry said it "sternly protests" the publication of the latest defense white paper and demanded the Japanese government immediately withdraw its territorial claim.

"We urge the Japanese ministry to realize it can't expect future-oriented development of our bilateral military relations unless Japan relinquishes its claim to Dokdo," the statement read.

"We will firmly deal with any attempts to damage the sovereignty of Dokdo."

To lodge complaint, the defense ministry summoned Hiroshi Kimura, a military attache at the Japanese Embassy to Seoul. Kimura was also summoned last year when the defense paper was released. (Yonhap News)