Chinese President Xi Jinping on Monday joined hundreds of people in an unusually high-profile ceremony marking the 77th anniversary of the start of war with Japan, while dancers in Beijing waved toy guns in commemoration.

Xi condemned those who "ignore the iron facts of history" in an indirect jab at Japanese Prime Minister Shinzo Abe, as Beijing seeks to draw attention to the past while it remains locked in a territorial dispute with Tokyo.

Xi's speech, broadcast live on state television, came alongside a deluge of articles in China's state-controlled newspapers marking the anniversary and criticising Japan for historical revisionism and moves towards potential remilitarisation.

The Sino-Japanese War, commonly known in China as the War of Resistance Against Japan, left 20 million Chinese dead, according to Beijing's estimates, and ended with Tokyo's World War II defeat in 1945.

Xi joined hundreds of soldiers, veterans and schoolchildren 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 triggered the war.

He unveiled a sculpture and praised the resistance of Chinese society against what he described as a "barbaric invasion".

"There are still a small number of people who ignore the iron facts of history," Xi said.

- 'Iron facts' -

He did not mention Japan or Abe by name. But Li Wei, chief Japan expert at the Chinese Academy of Social Sciences, a top government think-tank, said the reference was clear.

"It at least includes Shinzo Abe and people who deny history or are trying to gloss over history," she told reporters.

Japan has issued repeated apologies over its imperialist aggression in Asia before and during World War II.

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 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.

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.

- 'A pacifist nation' -

Japan's Chief Cabinet Secretary Yoshihide Suga, the top government spokesman, said the Chinese commemorations on Monday did "nothing to contribute to peace and cooperation in the region".

Tokyo remains repentant for its past aggression, Suga 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 daily "confessions" by Japanese war criminals, while state-run media have been intensifying criticism of Japan.

"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."

A dance troupe made up mostly of middle-aged women drew crowds in one of Beijing's busiest commercial districts Monday with a routine to commemorate the anniversary.

Wearing red berets, the women thrust toy guns into the air, marching in circles around two men representing Japanese soldiers, before forcing them to hand over their imitation weapons.

"It feels very righteous," said dancer Zhang Jinsu, 58.

"You have a pride in your nation, beating the devils," she added, using a common pejorative expression for Japanese soldiers.

Xi spoke after a two-day trip last week to Seoul, where discontent over Japan's perceived lack of sufficient repentance proved a key source of common ground with South Korean President Park Geun-Hye. Japan colonised the Korean peninsula from 1910-45.

The pair reportedly discussed the possibility of jointly marking the 70th anniversary next year of Japan's defeat, a proposal that Japan has dismissed as "utterly unhelpful".