SEOUL (AFP) - South Korea on Friday (March 18) protested Tokyo's approval of updated high-school textbooks that identify a cluster of small, Korean-controlled islets as part of Japanese territory.

"We deeply deplore that Japan has approved high-school text books that contain distorted views about history, including unjustified claims about our territory," South Korea's Foreign Ministry said in a statement.

The Dokdo islets, known as Takeshima in Japan, lie roughly halfway between South Korea and Japan in the East Sea (Sea of Japan).

"The Japanese government must understand that a correct teaching of history is a duty, not only to its future generations, but also to neighbouring countries that have suffered from Japan's past aggression," the statement said, urging a revision of the textbooks.

South Korea and Japan reached agreement at the end of last year on their dispute over wartime sex slaves that had soured relations for decades.

Japan offered a "heartfelt apology" and a 1 billion yen (S$12.1 million) payment to Korean women forced into Japanese military brothels during World War II.

Among the updated textbooks approved by Tokyo were six history books that carried content related to the so-called "comfort women" issue.

According to South Korea's Yonhap news agency, they stopped short of explicitly acknowledging the women's forced recruitment to frontline brothels.