The old woman had come to Tiananmen Square to draw the attention of China's rulers to her woes, but as the Communist elite met nearby to proclaim its commitment to a "people's democracy", police dragged her away.

In a scene repeated countless times a day across China, the woman cried as her documents were seized and she was led from the square as an elderly friend was bundled into a police car.

Just around the corner, China's ruling party gathered in the red-draped Great Hall of the People for a five-yearly congress that will usher in a new leadership.

On a stage lined with red and white flowers, and a giant Communist star shining in the centre of the ceiling, President Hu Jintao, the party's highest official and China's outgoing leader, addressed row after row of party bureaucrats in regulation dark suits.

In his last major speech as party leader, Hu touched on hot-button issues which his heir apparent Xi Jinping must address as he leads China for the next decade.

"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 said.

He warned that the party faces "collapse" if it fails to clean up corruption and curb Communist abuses of power.

But he also made clear that the party's idea of democracy did not equate to the West's boisterous multi-party elections, and the difference between the two systems was clear just outside the hall.

Hundreds of plainclothes policemen outside thronged Tiananmen Square -- scene of protests that culminated in a bloody crackdown in 1989 -- interspersed with fire crews equipped with extinguishers.

A string of Tibetans have set themselves ablaze to protest against Chinese rule of their traditional homelands in southwestern China.

They include four more in Sichuan province on the eve of the congress, and authorities were taking no chances of any incident in the heart of the capital that could embarrass the party during its most important political event.

There is a longstanding tradition in China of citizens petitioning the central authorities to intervene over their woes -- often issues of corruption and abuse of power -- but like many before them the two elderly women tried in vain to have their cause heard.

In a metro station nearby, another group of 20 to 30 apparent supplicants were surrounded by police before being taken away by bus.

"I have never seen such security measures in my whole life," said a Canadian tourist in the square, before his guide told him not to talk to journalists.

The Great Hall of the People stands at the apex of modern and ancient Chinese power, flanked by Mao Zedong's mausoleum to one side and the hulking mass of the Forbidden City, home to China's emperors for centuries, to another.

But even an innocuous petitioners' message can be unwelcome.

Zong Hua, 87, sat on a stool wearing an old Mao Zedong-era green military uniform, his chest covered with medals and a Mao badge on his cap.

"I came to Tiananmen because I am ill, I have a tumour," he said, pointing to his belly, before plainclothes police ushered away an AFP correspondent and demanded his notebook.

According to rights groups, hundreds of activists were placed under various forms of restriction including house arrest ahead of the congress, and a similar struggle has been waged online.

Censorship on China's equivalent of Twitter, Sina Weibo, has been stepped up, with searches for several soundalike terms for the meeting, previously used by internet posters to evade censors, blocked.

But inside the hall Chang Yaqiong, a delegate from Shaanxi province, said she was "very moved" by Hu's speech.

"After I go home I will take the spirit of this report and tell every one of us farmers that we must all show more love and support," she said.