SEOUL: South Korea said Friday its relations with Japan could suffer because of a newly published teaching manual that asserts Japanese claims over a group of islets under Seoul's control.

The new manual, released Friday as a guide for high school history teachers, says students should be given a deeper understanding of territorial issues, based on Japan's fair claim to certain geographic regions.

South Korean Foreign Ministry spokesman Moon Tae-young said the new manual "could cause negative effect on developing future-oriented relations between South Korea and Japan by infusing wrong territorial perceptions into Japan's future generations."

He said the move was regrettable.

Moon also stressed that the islands belong to South Korea "no matter what claims Japan makes."

Yonhap news agency reported that South Korea plans to call in Japan's ambassador to Seoul to file a protest. Moon said no decision has been made on whether to summon the envoy.

The rocky cluster of islets have long been a source of discord between Seoul and its former colonial ruler Tokyo. Seoul controls the outcroppings and has stationed police on them.

When Japan announced the middle school teaching manual last year, South Korea temporarily recalled its ambassador to Japan in protest.

Japan ruled the Korean peninsula as a colony from 1910-45.