Japan authorized a dozen new school textbooks renewing territorial claims to South Korea's easternmost islets of Dokdo on Wednesday in a move sure to sour the warming relations between the two neighbors.
The approval was seen by many South Koreans as a slap in the face as it came at a time when they have been pouring out sympathy and support for their former colonial ruler as it suffers from a devastating earthquake and tsunami.
The controversial books were part of the 18 geography, history and citizenship textbooks newly licensed for use at middle schools across Japan from next year.
The textbooks' approval represented a bolstering of Japan's claims over Dokdo because only 10 of the 23 textbooks currently in use in Japan have territorial descriptions of the East Sea islets, according to Seoul's foreign ministry.
In particular, the number of textbooks claiming South Korea is "illegally occupying" the islets rose from one to four, officials said.
South Korea planned to issue a statement of regret and call in Japanese Ambassador Masatoshi Muto to lodge protests. In Tokyo, South Korean Ambassador Kwon Chul-hyun plans to make a protest visit to Japan's foreign ministry, officials said.
But officials said they are not considering recalling the ambassador from Japan.
The government also planned to hold an inter-agency meeting to discuss steps reinforcing South Korea's sovereignty over the islets. Measures under consideration include launching a project to repair the aged heliport at Dokdo.
The education ministry plans to send a protest letter to Japan while demanding that incorrect descriptions in the approved textbooks be amended. In addition, the ministry plans to support a campaign to boycott the distorted textbooks, officials said.
Japanese school textbooks laying claims to Dokdo or glorifying the country's wartime past have long been considered a thorn in relations between the two countries as resentment over Japan's
1910-45 colonial rule of Korea still runs deep here.
South Korea considers Japan's sovereignty claims over the cluster of rocky outcroppings in the East Sea not as a territorial issue, but as a history matter related to the colonial rule as well as a sign that Tokyo has not fully repented for its militaristic past.
One of the bases for Tokyo's claims to Dokdo is a 1905 notice that a regional Japanese government issued to declare the islets as its territory. South Korea rejects the view as nonsense because the notice was issued when Korea was effectively a Japanese colony and it amounts to claiming that Korea is still its colony.
Korea regained independence in 1945, reclaiming sovereignty over its territory, including Dokdo and many other islands around the Korean Peninsula. Since shortly after the 1950-53 Korean War, South Korea has stationed a small police detachment on Dokdo.
Wednesday's approval is expected to cool the relations between Seoul and Tokyo that have warmed significantly since the Democratic Party of Japan came to power in 2009 and took symbolic steps to heal the lingering scars of its colonial rule.
Last August, Prime Minister Naoto Kan offered a renewed apology for the colonial rule, promising to return centuries-old royal Korean books to Seoul and take other steps backing up the apology.
It was considered the clearest apology that Tokyo has ever offered to Seoul.
Their ties improved further recently as South Koreans and their government set aside hard feelings about the colonial rule and provided full support for quake-stricken Japan in an unprecedented outpouring of sympathy and support for the historical rival and former colonial ruler.