Seoul has formally protested Japan’s claims over a pair of South Korean-controlled islets, after the education ministry unveiled curriculum guidelines that for the first time urge elementary and junior high schools to teach students the islets are “integral parts of Japanese territory.”

The protest was delivered on Tuesday after Chung Byung-won, director general of the Foreign Ministry’s Northeast Asia Affairs Bureau, summoned Hideo Suzuki, the minister and No. 2 official at the Japanese Embassy in Seoul.

South Korea’s Foreign Ministry, in a statement, criticized what it said was Japan’s “illegitimate” claim over the islets, known as Dokdo in Korean and Takeshima in Japanese, and called the move “deeply deplorable” and urged that it be “immediately retracted.”

“The Japanese government should realize that the revised curriculum guidelines may instill a wrong perception of territory into Japan’s growing generation, and cause a negative impact on development of future-oriented relations between South Korea and Japan,” it said.

The revised curriculum guidelines released by the education ministry earlier in the day call for clearly stating, from the fifth grade at elementary schools and in junior high schools, that the disputed islets are Japanese sovereign territory.