Chinese President Xi Jinping on Sunday hailed his Communist Party's zero Covid policies and graft crackdown as he opened a five-yearly Congress at which thousands of delegates were set to rubber stamp his bid to rule for a historic third term.

Xi walked onstage to thunderous applause from the roughly 2,300 hand-picked attendees who had gathered at Beijing's Great Hall of the People for the event.

In an opening address lasting about 100 minutes, Xi promoted and defended a wide range of policies under his rule and said the Congress was taking place at a "critical moment" for the country.

Xi celebrated the party's continued efforts to eradicate Covid -- which are placing heavy curbs on people's lives and is hammering the nation's economy -- as a major achievement.

He said the approach had "protected people's safety and health to the highest degree".

Xi also highlighted as a success his graft crackdown, which has seen thousands of people jailed and critics have said has been used to crush dissent and opposition to his rule.

Xi said the anti-corruption campaign had eliminated "serious latent dangers" within the Communist Party, the military and the state.

"The fight against corruption has won an overwhelming victory and has been comprehensively consolidated," he said.

Xi also focused on two of China's most sensitive security and sovereignty issues at the start of speech -- in relation to Hong Kong, after democracy protests were crushed there, and Taiwan.

He lauded Hong Kong's transition from "chaos to governance", while his vow to "never commit to abandoning the use of force" on the self-ruled island of Taiwan drew rapturous applause.

In a speech that mostly focused on domestic issues, Xi told the delegates that China would "actively participate in global governance on climate change".

Xi also reiterated that China opposed a "Cold War mentality" in international diplomacy, but made no mention of frayed relations with the United States.

"China... resolutely opposes all forms of hegemony and power politics, opposes the Cold War mentality, opposes interfering in other countries' domestic politics, opposes double standards," he said.

Xi did not reference the Ukraine war.

- Xi's unprecedented rule -

Should everything go to plan for Xi, the 69-year-old will be endorsed as the party's general secretary after the week-long meeting ends, cementing his position as China's most powerful leader since Mao Zedong.

If picked as party leader for another five-year term as expected, Xi is almost certain to be elected president at the annual meeting of China's National People's Congress in March.

Xi and the party's other top brass are likely to be unveiled on October 23, the day after the Congress closes.

In the highly choreographed, mostly closed-door conclave, the delegates will also pick members of the party's roughly 200-member Central Committee, which in turn selects the 25-person Politburo and its all-powerful Standing Committee -- the country's highest leadership body.

A heavy police presence was in place around Beijing early Sunday as authorities prepared for the Congress.

A fleet of buses whisked journalists and other attendees to a virtually empty Tiananmen Square and into the Great Hall of the People.

Participants navigated a string of security checks before entering the hall, where a giant hammer-and-sickle emblem hung over the stage on which top leaders are due to be seated.

"Long live the great, glorious and correct Chinese Communist Party," blared one of the bright red banners adorning the hall.

In the lead-up to the Congress, China's internet censors removed virtually all references to reports of a rare protest in Beijing that involved banners denouncing Xi and the country's Covid policies.

Video footage and photos shared on social media on Thursday appeared to show a protester draping two hand-painted banners on the side of a bridge with slogans criticising the Communist Party's policies.