President Xi Jinping addresses a state commemoration for China's first National Memorial Day for Nanjing Massacre Victims in Nanjing, east China's Jiangsu Province, Dec. 13, 2014. [Photo/Xinhua]

BEIJING - China on Saturday observed its first National Memorial Day for Nanjing Massacre Victims, and the commemorative service gained worldwide media attention.

Singapore's South China Morning Post reported that Chinese President Xi Jinping unleashed at a solemn ceremony some of his sharpest words to date against Japan's wartime atrocities in China more than seven decades ago.

Xi and others gathered at a memorial hall in Nanjing, where 77 years ago invading Japanese soldiers slaughtered more than 300,000 people, mostly unresisting civilians, the newspaper said.

The newspaper quoted Xi as calling the massacre "a horrendous crime against humanity and a very dark page in the history of mankind" and stressing that history should not be altered with the passing of time, and facts not erased by crafty denial.

French news agency AFP noted that China for the first time held a national day of remembrance for the Japanese military rampage that killed 300,000 people, and cited Xi as saying that no one can deny the Nanjing Massacre.

The crowd, who attended a ceremony in Nanjing to mark the 77th anniversary of the massacre, sang China's national anthem and observed a moment of silence as a siren symbolizing grief blared and the Chinese national flag flew at half-mast under clear skies, AFP noted.

In an online report, BBC said Xi criticized Japanese nationalists for denying Japan's wartime atrocity in Nanjing.

Xi told survivors that to deny a crime was to repeat it, but he insisted that the ceremony was to promote peace, not prolong hatred, BBC said.