Xi and a cast of hundreds of soldiers and schoolchildren gathered for a ceremony on the edge of the capital to mark the Marco Polo Bridge incident, a skirmish between Chinese and Japanese troops on July 7, 1937 that served as a pretext for Tokyo's forces to seize Beijing and triggering the Sino-Japanese war.
The event, carried live on state television, came amid a deluge of articles in China's state and Communist Party-controlled media linked to the anniversary and criticising Tokyo for historical revisionism and moves towards potential remilitarisation.
The conflict, commonly known in China as the War of Resistance Against Japanese Aggression, left 20 million Chinese dead, according to Beijing's estimates.
It ended with Tokyo's World War II defeat in 1945.
Flanked by ageing war veterans and young students, Xi unveiled a slab-like sculpture marking the start of the conflict and praised the resistance of all sectors of Chinese society against what he described as Japan's "barbaric invasion" aimed at "annexing" China. Japan had already invaded Manchuria in 1931.
"There are still a small number of people who ignore the iron facts of history," Xi said, although he avoided mentioning Japan or Abe by name.
"History is history and facts are facts. Nobody can change history and facts," he added. "Anyone who intends to deny, distort or beautify history will not find agreement among Chinese people and people of all other countries." In Taiwan dozens of slogan-chanting protesters tore up Japanese military flags and portraits of Abe, attempting to set fire to them before they were stopped by police.
"It at least includes Shinzo Abe and people who deny history or are trying to gloss over history," she told reporters.
Xi's remarks come as Tokyo and Beijing are locked in a territorial dispute in the East China Sea, and after Japan last week announced a reinterpretation of its pacifist constitution that Beijing argues could send the country down the path to remilitarisation.
Japan has issued repeated apologies over the war. But frequent statements by conservative politicians and public figures seemingly casting doubt on them and calling into question factual issues have increased suspicion in China and some other countries such as South Korea.
A visit by the democratically elected Abe to a controversial Tokyo shrine that memorialises Japan's war dead, along with convicted World War II criminals, in December only added fuel to the fire.
Japan's Chief Cabinet Secretary Yoshihide Suga, the top government spokesman, said in response to Monday's commemorations: "China unnecessarily turning an historical issue into an international one does nothing to contribute to peace and cooperation in the region." Tokyo remains repentant, he stressed.
"There is no change to the position of the Japanese government regarding historical issues stemming from World War II, and our nation's path as a pacifist nation since the war has been highly regarded in the international community." Ahead of the anniversary, China last week began releasing a daily "confession" by Japanese war criminals set to go on for 45 days, and state-run media have been intensifying criticism of Japan. State TV on Monday showed black and white footage of the emotional testimony of a woman at a 1956 war crime proceeding.
Xi spoke after a two-day trip last week to South Korea, where he said the "Japanese militarists carried out barbarous wars of aggression against China and Korea".
Xi and South Korean President Park Geun-Hye, who has criticised Tokyo over history - Japan colonised the Korean peninsula from 1910-45 - reportedly discussed cooperating on the 70th anniversary next year of Japan's defeat.
Japan annually recalls the atomic bombings of Hiroshima and Nagasaki on August 6 and August 9, respectively, in ceremonies attended by the prime minister, followed by another remembering its surrender on August 15 in which the emperor also traditionally participates.
"Japan's depiction of the war did not make its people feel ashamed of that history," the Global Times, a newspaper with close links to the ruling Communist Party, said in an editorial Monday.
"Rather, it generated so much pathos that many feel aggrieved toward the losses their country suffered and Japan's status as a defeated nation."