SOME 100,000 TAXI DRIVERS BEGAN plying Beijing's roads in smart new yellow shirts and striped ties this weekend in the latest effort by the government to spruce up the city's image.

Red Chinese and white Olympic flags hang on many taxis, private cars and buildings amid a growing, but still mild, Olympic fever in the city. Many taxi drivers hope to earn extra income from the tens of thousands of athletes, spectators and journalists flooding into the city to stay at top hotels and the Olympic villages in Beijing's suburbs.

Beijing's two most spectacular Olympic venues are attracting hundreds of sightseers nightly, forcing the police to send crowd control officers and divide a footbridge that offers one of the best views.

Floodlighting makes the silver-painted steel structure of the Bird's Nest Olympic stadium appear predominantly red and yellow, while intense blue lighting highlights the bubble-effect surfaces of the Water Cube aquatics centre.

Many visitors park their cars in the surrounding streets, photographing each other in front of the venues, which are always at least 200 yards away, or pressing their lenses through the wire fences to get an unobscured shot.

Behind the fences workers put the finishing touches to lawns and flower beds while hundreds of paramilitary police patrol the perimeter.

Just before midnight on Friday, a group of road workers from the eastern province of Shandong sat near the Water Cube taking a breather before continuing their all-night shift. Close by were several groups of young people, some sitting cross-legged on the tarmac and staring at the magnificent architecture as if lost in meditation or worship.

When the Olympics open next Friday, at 8.08pm on the eighth day of the eighth month of 2008, all the eights will symbolise the prosperity of the Chinese nation. The stunning opening ceremony is orchestrated by award-winning film director Zhang Yimou, with fireworks by renowned artist Cai Guoqiang.

But you will not see the hundreds of thousands of workers who have made it all possible.

"We will be going home before the 8th," said one of the road workers at the Water Cube when asked if he would see the opening.

Far away from the Olympic stadium is an area in the south of the city unseen by most visitors, and one which is undergoing a very different kind of Olympic makeover.

The grey brick walls of the Beijing Financial Assistance Management Centre are topped with metal spikes and barbed wire, like many official buildings in China's capital. But rather than protecting state property, this barbed wire is meant to keep people inside the centre, whose bureaucratic-sounding name masks its true function.

Residents in Beijing's Majialou area know the collection of low-rise buildings as the "petitioners holding centre". It is the last place that many petitioners see in Beijing, as most leave here in the custody of police for their home areas, where they will sometimes face fines, beatings, and even detention.

The Majialou centre, and an unknown number of smaller detention centres usually set up in hostels by local governments from outside Beijing, operate as "illegal black jails", said Hu Xingdou, an economist at the Beijing Institute of Technology.

"These are all illegal; I hope the central authorities will investigate."

The illegal detention centres have been busier than usual recently. Authorities evicted an estimated 4000 petitioners from a shanty town not far from Majialou last year in the run-up to a key congress of the Communist Party in Beijing, claiming the land was needed for a road project.

At least 1500 more petitioners were taken into custody in a pre-Olympic purge this year, the Hong Kong-based Information Centre for Human Rights and Democracy said.

"No-one is contacting me now, not like before the Olympics," Hu said of the petitioners.

Not far from Majialou, clustered around the Yongdingmen long-distance bus station and the Beijing South railway station, are run-down hostels where many petitioners bed down for weeks, or sometimes years, while trying to get legal cases and grievances heard by China's highest authorities at nearby petitions offices. Most petitioners have no hope of resolving their problems, Hu said, because the judiciary lacks independence from the Communist Party.

"I've written to the national leaders several times, but they never reply", said Hong Li, a petitioner in her fifties from central China.

Hong Li, which is an assumed name for protection, said she made her first trip to Beijing in 2000 to petition over a 25-year-old property dispute. She began her latest visit in July and has managed to avoid arrest so far.

Hundreds of other petitioners have not been so fortunate, falling into the net cast by police to remove them from Beijing's streets before the Olympics.

At the end of a Yongdingmen alley on Thursday about 30 people, many of them plain clothes police, stood in front of two rusty gates before the afternoon opening of the petitions office of the Supreme People's Court. One policeman waved his arm in front of two new arrivals halfway down the alley. "Do you want to see the leaders?" he said.

US-based Radio Free Asia this week quoted several petitioners as saying staff at the court petitions office were allowing people to enter the compound but then taking them out through another gate and on to detention centres.

Hong said she also knew petitioners who had seen the new policy in action. "Once you've gone in, you don't come out", she said.

Hu and lawyer Ren Hua earlier this year published a report based on interviews in Beijing with 400 petitioners, 45% of who said they had been detained or imprisoned and 30% said they had been beaten.

Police vans from Shandong, Heilongjiang and other distant provinces still drove through the alleys near the petitions offices on Thursday.

"There were 20 or 30 vehicles to collect us petitioners from Heilongjiang", one petitioner told Radio Free Asia.

"There were People's Armed Police and People's Liberation Army soldiers there too, all lined up."

Hong was worried that police might have tailed her after she spoke to a foreign reporter. "That waitress is spying on us, isn't she?" she asked at a cafe near the bus station.

Hong is one of Beijing's underclass of perhaps two million migrants, mostly construction workers, restaurant staff, shop assistants, masseuses, cleaners, rubbish recyclers and nannies. She said she often sleeps outside during her long visits to Beijing.

She avoids high security areas such as the Olympic venues and Tiananmen Square, the symbolic centre of the city.

"We daren't go to Tiananmen Square, they're arresting people there, we're all afraid", she said.

Amnesty International this week renewed its criticism of China's pre-Olympic crackdown on petitioners, dissidents and rights activists.

"The Chinese authorities have broken their promise to improve the country's human rights situation and betrayed the core values of the Olympics", Amnesty said in a report.

"In the run-up to the Olympics, the Chinese authorities have locked up, put under house arrest and forcibly removed individuals they believe may threaten the image of stability' and harmony' they want to present to the world."

Roseann Rife, Amnesty's Asia-Pacific deputy director, said: "By continuing to persecute and punish those who speak out for human rights, the Chinese authorities have lost sight of the promises they made when they were granted the games seven years ago. The Chinese authorities are tarnishing the games."

The International Olympic Committee has been drawn into a row over internet access in China, where the websites of foreign media, rights groups and religious groups are blocked.

All foreign websites are accessible in the Olympic media centre, but other banned sites remain blocked, prompting some journalists and rights groups to criticise the IOC for not pushing China hard enough.

The row stems from confusion over what China actually promised to do to its Great Firewall during the games.

"Following discussions, the IOC has held with the organisers of the Beijing 2008 Olympic Games on the difficulties experienced this week in accessing some websites, the IOC is pleased to see that the issues are quickly being resolved", the IOC said on Friday.

"The media should be seeing a noticeable difference in accessibility to websites that they need to report."

But Bocog,the games organisers, made it clear access to websites such as those of the banned Falun Gong spiritual movement would not be allowed.

"If a few websites are difficult to browse, it's because they have spread content that is banned by the Chinese laws," a Bocog spokesman said.

"The Chinese laws forbid anyone to spread illegal information, such as preaching an evil cult like the Falun Gong, or do anything that harms national interests through the internet", the government's official Xinhua news agency added yesterday.

To make sure that Falun Gong members and right activists do not gather on Beijing's streets the city has mobilized about 500,000 "social volunteers" to help maintain security and join about 100,000 police, 200,000 security guards as well as soldiers.

Another 400,000 volunteers will be scattered across the city mainly to assist visitors, 500,000 people will help control traffic, and some 100,000 trained volunteers will work directly for the organisers during the Olympics.

The government says it is most worried about the threat of a terrorist attack from Muslim separatists in its far western region of Xinjiang. Police helicopters regularly swoop over the city and anti-aircraft missiles are deployed not far from the Olympic Green.

Its concern about foreigners travelling to Beijing to protest, especially over Tibet and Darfur, resulted in the expulsion of the British Tibetan woman Dechen Pemba in early July. But China has promised to allow some sanctioned protests in three parks, all far from the Olympic games area.

Hu said some petitioners may have evaded the security net and may reappear during the Olympics, with the government perhaps allowing some of them into the three parks.

"Probably some of them are now hiding in the suburbs and don't take part in public activities," he said. But Hu said he was concerned that the resolute anti-government sentiment of some petitioners, and the recent pressure applied on them by officials and police, could prompt violent protests.

He said: "I'm a little worried that some of them could take some violent action during the Olympics."