"Anyone who tries to deny the massacre will not be allowed by history, the souls of the 300,000 deceased victims, the 1.3 billion Chinese people, and all people who love peace and justice in the world," Xi said while speaking at the first National Memorial Day for Nanjing Massacre Victims.
The Chinese and Japanese people should live in friendship from generation to generation and make joint efforts to contribute to the peace of humanity, he said.
"We should not bear hatred against an entire nation just because a small minority of militarists launched aggressive wars. The responsibilities for war crimes lie with a few militarists, but not the people. However, we cannot at any time forget the severe crimes committed by aggressors," he said.
The Nanjing Massacre, committed by Japanese aggressors, was one of three major massacres during WWII.
It was an atrocious anti-human crime and a dark page in the history of humanity, Xi said in his sharpest comments against Tokyo since he came to power last year.
Japanese troops captured Nanjing, then China's capital, on December 13, 1937 and started a 40-odd-day slaughter, state-run Xinhua news agency report said.
More than three lakh soldiers, who had laid down their arms, and civilians were murdered and about 20,000 women were raped, it said.
The ceremony was held at the memorial hall for the massacre victims in China's eastern city of Nanjing.
"The purpose of the memorial ceremony for Nanjing Massacre victims is to recall that every good hearted person yearns and holds a firm stance of peace, but does not try to prolong hatred," Xi said.
Military and Presidency struck a hard line against Japan over the disputed islands issue besides Japan's war crimes which aroused nationalistic passions among Chinese people.
After a prolonged estrangement, Xi met Japanese Prime Minister Sinzhou Abe for the first time when he came to attend the APEC leaders meeting here last month.
China which overtook Japan as the second largest economy in 2011 shares a bitter relationship with Tokyo especially after the dispute between the two over the disputed islands in East China Sea escalated since 2012.
Xi, along with Xia Shuqin, an 85-year-old massacre survivor, and a school child, dedicated a 'ding,' a type of ancient Chinese cauldron symbolizing state power and prosperity, to the victims of the massacre.
The three-legged bronze ding will be permanently placed at the square of the hall.
Xi expressed thanks to the foreigners who had protected Nanjing residents and recorded the atrocities of the Japanese invaders, despite the risks.

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