Chinese President Xi Jinping lauded his country as a major power and a force for world peace Thursday as he presided over a spectacular military parade marking the 70th anniversary of Japan's defeat in World War II.

With concerns rife over China's rise, Xi announced that the People's Liberation Army -- the world's largest military -- would be reduced by 300,000 personnel, although the defence ministry said the cuts would mainly fall on outdated units and non-combat staff.

"War is the sword of Damocles that still hangs over mankind," Xi said. "We must learn the lessons of history and dedicate ourselves to peace."

But moments later new missiles dubbed "carrier-killers", which experts say could change the balance of power with the United States, rolled through the square, in an unmistakable show of strength.

The mixed messages drew a rebuke from Japan which said it was "disappointed" by Xi's speech for focusing too much on the past and for its lack of "rapprochement" between the Asian powers, the world's second- and third-largest economies.

With disquiet growing over China's increasing assertiveness in territorial disputes, most Western leaders stayed away from the extravaganza in Tiananmen Square, where Chinese troops crushed democracy protests in 1989.

After a 70-gun salute, thousands of troops marched in formation through the square, with tanks and missiles following, while nearly 200 aircraft performed a flypast in blue skies overhead.

The immaculate, choreographed ranks of soldiers included a detachment from Russia, whose President Vladimir Putin was the highest-profile foreign guest.

China has repeatedly insisted the parade was not aimed at any particular country, including Japan, which it says is insufficiently contrite over wartime atrocities.

"The unyielding Chinese people fought gallantly and finally won total victory against the Japanese militarist aggressors, thus preserving China's 5,000-year-old civilisation and upholding the cause of peace," Xi said.

He described the eight-year conflict, in which historians say 15 to 20 million Chinese died, as "a decisive battle between justice and evil, between light and darkness" and that the victory had "re-established China as a major country in the world".

- 'Game changer' -

Decades of double-digit budget increases have transformed China's military, giving Beijing the confidence to push a programme of artificial island building in the South China Sea and vigorously proclaim its sovereignty over disputed outcrops controlled by Japan.

The equipment on show for the first time at the parade included DF-21D missiles, an anti-ship ballistic missile that could be used in the Pacific to target US aircraft carriers.

"There's no doubt that it will be a game changer" if it performs as claimed, said Jon Grevatt, Asia-Pacific defence analyst at IHS Jane's.

For decades, Washington's carriers have been the core of its ability to project power around the world and a commentator on Chinese television described the weapon as a "trump card".

The parade came as five of China's vessels were spotted in the Bering Sea off Alaska for the first time, according to the Pentagon.

Under Xi, Beijing is moving farther away from former leader Deng Xiaoping's dictum to "hide one's capabilities, bide one's time" and taking harder lines, both externally and against domestic opponents.

Xi's announcement of troop reductions was widely expected and comes after around two million personnel have been cut from the PLA since the 1980s.

On its website China's defence ministry said the military would be "slimmer but more capable, and their composition more scientific".

It was "part of President Xi Jinping's continuing efforts to enhance the efficiency of the military", Grevatt told AFP.

- 'Very nationalistic' -

Putin was given a prominent position next to Xi on the rostrum, as were ranks of former Chinese leaders, including Jiang Zemin and Hu Jintao.

Shaking hands with Xi were Sudan's Omar al-Bashir -- indicted by the International Criminal Court -- and authoritarian Belarussian President Alexander Lukashenko, who brought one of his sons.

More mainstream guests included South Korea's Park Geun-Hye, whose country was colonised by Japan, Jacob Zuma of South Africa -- which with China is part of the BRICS groups of major emerging economies -- and UN Secretary General Ban Ki-moon.

John Delury, an expert on China at Yonsei University in Seoul, told AFP the limited international guest list was because "it's a very nationalistic and militaristic event".

"Across Asia and certainly in the United States there are all these concerns about the hard power side of China's rise," he said.

Chinese authorities mobilised hundreds of thousands of Beijing citizens and closed roads across much of the city centre, shuttering airports and curtailing pollution-spewing factories and vehicles to ensure blue skies.

The Communist Party uses nationalism as part of its claim to legitimacy, and Xi stressed the role of "the Chinese people" in the war, obscuring the Communist Party's rivalry with the then-governing Nationalist forces of Chiang Kai-shek, which it later defeated.

Among other wartime allies, he only named the Soviet Union and did not mention the United States, whose atomic bombing of Japan is widely seen as ending the conflict.