China's president Thursday warned the Communist Party faces "collapse" if it fails to clean up corruption and called for an economic revamp as he opened a congress to inaugurate a new slate of leaders.

The week-long party congress will end with a transition of power to Vice President Xi Jinping, who will govern for the coming decade amid growing pressure for reform of the communist regime's iron-clad grip on power.

The party's outgoing general-secretary, President Hu Jintao, delivered his starkest warning yet about fighting rampant corruption following a top-level murder and graft scandal involving former regional boss Bo Xilai.

"If we fail to handle this issue well, it could prove fatal to the party and even cause the collapse of the party and the fall of the state," Hu told more than 2,200 delegates inside Beijing's cavernous Great Hall of the People.

At the congress, which is held every five years, Hu also positioned the world's second-largest economy for a more assertive role as he insisted China should be a "maritime power" that "resolutely" protects its interests.

Heading into the 18th party congress, China has been skirmishing with Japan and other Asian neighbours over a slew of territorial disputes, and flexing its growing military muscles to the disquiet of the United States.

"We must continue to make both active and prudent efforts to carry out reform of the political structure and make the people's democracy more extensive, fuller in scope and sounder in practice," Hu also said.

Without naming Bo, the president added that the party "must make sure that all are equal before the law".

But Hu's call for political reform contrasted with the treatment meted out to would-be protestors outside the Great Hall of the People on Tiananmen Square, where the army gunned down massed ranks of pro-democracy students in 1989.

An AFP reporter saw two elderly women hustled away from the vast esplanade as they attempted to present petitions against wrongdoing by their local communist leaders.

One woman was bundled into a police van and the other led away sobbing as police shooed away onlookers at the scene. In a metro station near the square, another group of up to 30 petitioners were surrounded and taken away by bus.

Hundreds of activists have been put under house arrest, rights groups say, while Beijing taxi drivers have been told to lock their back windows apparently to prevent passengers from throwing out flyers with political messages.

On China's wildly popular social media websites, search terms related to the congress were censored but a few caustic responses to Hu's speech got through. "What a joke. My high school essays were better than that!" one posting said.

In his 90-minute address, Hu also stressed that China must recalibrate its export- and investment-led growth model, after years of breakneck economic expansion that experts warn is unsustainable.

"In response to changes in both domestic and international economic developments, we should speed up the creation of a new growth model and ensure that development is based on improved quality and performance," he said.

Communist leaders including Premier Wen Jiabao -- who is due to step down in March as part of the leadership transition -- have long been calling for China to rebalance its economy by fostering domestic consumer spending.

That would help redress China's swollen trade surpluses, which have been an irritant to the West for years and cast the country as the foreign bogeyman of the just-concluded US presidential campaign.

But the economy still rests heavily tilted towards export-led growth. And with Western markets reeling, China in the latest quarter posted its slowest rate of growth since the global financial crisis in 2009.

The congress will end next week with the installation of Xi as the party's new general-secretary, and he is in line to succeed Hu as state president next March.

But Xi, the son of a revolutionary hero who has been Hu's heir apparent since 2007, will take over at a challenging time given the rare economic slowdown, amid demands for change from the country's vocal netizens.

A state-run newspaper published a survey Wednesday suggesting eight out of 10 Chinese in major cities want political reform of some sort.

The contrast with how the United States manages its political affairs was laid bare with President Barack Obama's re-election triumph, and did not go unnoticed among commentators on China's "weibo" chat sites.

Behind closed doors, Communist Party leaders appear to have settled on the new line-up of the Politburo Standing Committee, China's highest decision-making body, which will be unveiled when the congress ends on November 14.

The committee will be steered by Xi, 59, who has previously headed some of China's most economically dynamic and reform-minded areas. But in the opaque communist system, little is known about his personality or policy inclinations.