Beijing: China said on Tuesday it had lodged a formal protest with Japan over new Japanese school text books which it said distorted the history of Japanese atrocities in China and reasserted a Japanese claim to a group of disputed islands.

China, the world’s second-largest economy, and Japan, the third-largest, have a difficult history, with relations strained by the legacy of Japan’s aggression before and during World War Two and conflicting claims over a group of uninhabited East China Sea islets.

Japanese media say some of the textbooks approved for use from April 2017 describe the disputed islands as being inherently part of Japan. The books also revise some references to the 1937 Nanjing Massacre.

Chinese Foreign Ministry spokeswoman Hua Chunying, asked about the text books at a daily news briefing, said China was extremely concerned and had lodged ‘stern representations’ with Japan.

‘No matter what steps Japan may take to promote and market their mistaken position it cannot change the basic reality that the Diaoyu islands belong to China,’ she said, referring to what Japan calls the Senkakus.

‘The Nanjing massacre was an atrocity carried out by the Japanese militarists when they invaded China. The evidence is cast iron and a conclusion was reached long ago about it. This whitewashing and censoring by Japan in these text books again shows that Japan is unwilling to face up to historical mistakes.’

China consistently reminds its people of the 1937 massacre in which it says Japanese troops killed 300,000 people in its then capital.

A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place at all.

Chinese school text books also have their own political slant, following the ruling Communist Party’s line on issues like Tibet and Taiwan, and not mentioning highly sensitive events such as the bloody 1989 crackdown on pro-democracy demonstrators around Tiananmen Square.