At least seven street cleaning trucks drove repeatedly up and down the street, spraying water and keeping crowds pressed to the edges.

Uniformed police, security guards and sanitation workers with armbands that said 'Public Security Volunteer' urged pedestrians to move along.

Despite the heavy police presence, large crowds turned up near a McDonald's restaurant on the street at about 2pm, as the anonymous posting that appeared on US-based Boxun.com urged.

But it was virtually impossible to distinguish those who had shown up for the rally from the shoppers, tourists and passers-by in the street, as no one picked up flowers, unfurled banners or chanted slogans like some demonstrators had done a week ago.

The street was temporarily blocked for about 30 minutes from about 2.30pm when the crowds continued to increase.

People at dozens of shops along the street were barred from walking out. Some shop assistants urged shoppers to avoid the street because 'it was off-limits due to security reasons'. People who wanted to use the pedestrian street were asked to show their identification.

Almost all connecting streets were also condoned off and some reported their mobile phone signals were cut off when they were in the area.

Dozens of plain-clothes officers were also seen inside the McDonald's and a nearby KFC, a popular chicken restaurant also designated as a rally site, taking photos of customers with cameras.

At least 10 foreign correspondents, including those from the BBC, Voice of America and the German broadcasters ARD and ZDF, were detained by police on the ambiguous complaint that they were violating Beijing's reporting regulations, witnesses said. Two Hong Kong TV reporters were also briefly detained.

Several foreign media outlets were warned to stay away from the planned rallies or blocked from entering the street after Beijing issued a stern warning on Friday urging foreign journalists to abide by Chinese laws. Beijing has also markedly stepped up internet censorship and cracked down on dissidents over the past week in a response to the on-line calls for rallies.

Street sweepers were seen involved in manhandling foreign journalists who tried to take photos after the street was cordoned off.

'Why did they have to use force against those foreign reporters?' an onlooker asked. 'I am really curious what they will do in the future and how much it would cost to stage such massive force every week.'

Another man who said he came to show support for the peaceful rally laughed at what he called a gross overreaction. 'We just came to criticise the government in a constructive way and no one wants to overthrow the one-party rule with force. Why are they so afraid of the people?'

In Shanghai, there were also scuffles and tense scenes as police clashed with several hundred probable protesters loitering at the entrance to the Peace Cinema in the Raffles City mall, one of the city's most popular shopping venues.

At least one protester was detained a few minutes before 2pm, and some witnesses said five or six demonstrators were taken away by police during the 90 minutes the gathering lasted.

Scores of police patrolled the 100-metre stretch of pavement outside the mall, which faces People's Square in the centre of the city, blowing shrill whistles and manhandling pedestrians as they constantly attempted to break up the crowd and spectators. They were assisted by several small street-sweeping vehicles that drove back and forth through the throng.

Many onlookers professed ignorance, but the many who arrived with a purpose - an odd, male-dominated mix of elderly petitioners and young tech-savvy activists, speaking in hushed tones and making furtive glances at the police - were determined to make their point.

'I heard about this online so I came to lend my support. I just want to express my attitude,' said a well-dressed young man recording the scuffles on his mobile phone and speaking in English in an attempt to avoid police understanding his comments. 'That is, that I am dissatisfied with the government.'

At about 2.10pm, a scuffle outside the mall's Starbucks cafe between police and a member of the crowd they appeared to be trying to detain sparked a passionate response.

A guttural roar spread instantly through the assembled pedestrians and the crowd surged forward on the police almost as one, demonstrating that the vast majority knew exactly what was going on.

In Guangzhou, uniform and plain-clothes police flocked to the People's Park and the Tianhe Sports Stadium. The stadium's front entrance, nominated as this week's meeting spot, was blocked by police barriers. Officers were seen guarding key spots and patrolling the area. A man who identified himself as a tourist was questioned outside the stadium for photographing police.

Professor Jean-Pierre Cabestan, head of Baptist University's political science department, said that even though there were few protesters, the authorities deployed a lot of police because they knew exactly the level of discontent. 'In an authoritarian regime, the (state) security knows better than anyone else the mood of society and how the mood is changing.'

Additional reporting by Zhuang Pinghui, Priscilla Jiao and Ed Zhang