Japan's Education Ministry on Wednesday approved a spate of junior high school textbooks that describe Korea's Dokdo islets as Japanese territory. The four geography, seven history and seven ethics books will be used in schools from April of next year, and 12 of them (four geography and seven history plus one ethics book) claim Dokdo is Japanese.

The number of textbooks claiming that Korea illegally occupies the islets rose from one to four.

In one ethics textbook published by Tokyo Shoseki, which was used by 61.1 percent of junior high schools in Japan as of November 2009, Dokdo is already described as being sovereign Japanese territory illegally occupied by Korea.

The covers of new Japanese middle school textbooks for history and social studies /Yonhap

However, none of the textbooks mention the plight of Korean and other Asian women who were forced to serve as sex slaves for Japanese soldiers during World War II.

The announcement was part of a regular review process that happens every four years. Senior high school textbooks are up for review next year, and they too are likely to assert Japan's territorial ambitions.

More diplomatic friction looms next month, when Tokyo unveils its Diplomatic Blue Book, and in July, when its new Defense White Paper is published. Both are expected to include the same claims.

Foreign Minister Kim Sung-hwan summoned Japanese Ambassador Masatoshi Muto on Wednesday to lodge a protest against the new textbooks.