China expressed grave concern Tuesday over Japan's newly-approved textbooks that stepped up Tokyo's claim over the East China Sea islands at the center of a territorial dispute between the sides.
  

"We are gravely concerned about what is happening in Japan," Chinese foreign ministry spokeswoman Hua Chunying told reporters during a regular press briefing, when asked about the new Japanese history textbooks.
  

"History is history. It cannot and should not be allowed to be changed willfully," Hua said.
  

The new textbooks also changed the word "massacre" in reference to the mass-killing of Chinese people in Nanjing in 1937 to the word "incident."
  

Bilateral relations between China and Japan have been always shaky because of their bitter shared history, but deteriorated in recent years over the disputed islands, known as Senkaku in Japan and Diaoyu in China, in the East China Sea.
  

The new Japanese textbooks also sparked protests from South Korea because they bolstered Tokyo's claim to South Korea's easternmost islets of Dokdo.
  

Earlier in the day, South Korea's Foreign Ministry summoned Kenji Kanasugi, a minister at the Japanese Embassy in Seoul, to lodge a complaint with the Japanese government over the new textbooks. (Yonhap)