Beijing's vast Tiananmen Square was a sea of red flags, propaganda banners and police uniforms Wednesday as China's ruling Communist Party prepared to gather nearby to appoint its new leaders.

More than 2,000 delegates will attend the five-yearly party congress that opens on Thursday. At its close a week later, it will unveil the top brass who will govern the most populous country and second-largest economy for the next decade.

Visitors to the square -- a popular tourist site near the regime's nerve centre and the scene of 1989 democracy protests crushed by authorities -- submitted themselves and their belongings, even water bottles, to security checks.

A towering floral arrangement stood 15 metres (49 feet) high at the centre of the square -- its massive scale matching that of the nearby Great Hall of the People, the Stalinist-style building that will host the congress.

Officers kept fire extinguishers on hand, possibly fearing repeats of dozens of self-immolations by Tibetans in western China in protest at Chinese rule.

Delegates from around the country are meant to represent the world's largest political party with 82 million members. Yet their main task will be to rubber-stamp a leadership succession carefully chosen by the party elite.

The week-long event begins on the eighth -- considered an auspicious number in China. The congress that installed President Hu Jintao as party chief 10 years ago started on the same date, while the Beijing Olympics opened on 08/08/2008.

The city has deployed a vast range of security forces -- military police, regular police, plain-clothes officers as well as 1.4 million volunteers, often retirees, wearing red armbards.

The highly-visible security presence put Indian tourist Nidhi Verma on edge. "All these policemen," she said while walking along the edge of the square. "I was not even sure it was allowed to take pictures."

The security extends even further. Objects recently banned include fruit knives, balloons, ping-pong balls (which might bear "reactionary" messages) as well as toy planes and helicopters, according to reports.

Pigeon owners have been warned to lock up their birds and concerts and gatherings in public parks have been halted as have boat rides on lakes near Zhongnanhai, a private residential compound for senior leaders.

On the Avenue of Eternal Peace along the northern edge of Tiananmen, buses were instructed to lock their windows, possibly to prevent passengers from throwing flyers with political messages into the square.

Taxi drivers were told to deactivate their back windows apparently for the same reason -- and to watch out for potential protesters attempting to reach the square.

Petitioners coming to the capital to lodge complaints about injustices have been sent away in recent days, as have prominent critics of the regime.

Hundreds of activists have been placed under various forms of restriction including house arrest ahead of the congress, rights groups have said.

Prostitutes and migrant workers have also been told to leave, according to city residents.

At the same time oversized signs erected among flowerbeds at Tiananmen Square sought to remind passers-by that people are at the core of the party's mandate.

"Thoroughly apply scientific development theory," one said in large red script, referring to Hu's concept of balanced economic growth meant to bolster the less well-off.

"Improve the livelihood and well-being of the people," read another.