Olympics-Torch cheered in Tiananmen, protesters held

* Torch carried through Beijing with two days to go

* Four foreigners arrested for Tibet protest

* First event, women's soccer, starts in evening

* Smog persists despite cleanup

* Team Darfur co-founder denied visa

By Paul Majendie and Guo Shipeng

BEIJING (Reuters) - Euphoric crowds chanting "Go Olympics, Go Beijing" cheered the Olympic flame through Tiananmen Square on Wednesday at the end of its troubled global relay.

Two days before the Games start, four foreign protesters sought to spoil the party mood for China's Communist government by unfurling "Free Tibet" banners from electricity poles near the main Olympics stadium, state media said.

Police rushed in to detain them.

Most of the 10,500 athletes from 205 countries have now arrived. The first competition -- women's soccer -- was to start on Wednesday night ahead of Friday's Games opening, giving Chinese fans the first chance to show their Olympics fervour.

Men's soccer, which has drawn the likes of Argentina's Lionel Messi and Brazil's Ronaldinho, starts on Thursday.

Then at the weekend, the eagerly awaited swimming competition begins in the new "Water Cube" pool, a shimmering landmark for the Olympics. American Michael Phelps is seeking to smash compatriot Mark Spitz's 1972 record of seven golds in one Games.

In Tiananmen Square, a Beijing landmark best-known to the world for the crushing of 1989 student protests, one of China's most famous sportsmen, 7ft 6in basketball player Yao Ming, held the flame above a sea of beaming faces.

Though not fully fit, NBA player Yao will lead China's team when basketball starts at the weekend, also featuring a U.S. squad pumped to avenge missing gold in Athens four years ago.

Children wore "I Love China" T-shirts and workers waved flags and pom-poms, while drums and cymbals resounded around Tiananmen under a portrait of late revolutionary leader Mao Zedong.

China's first man in space, Yang Liwei, also took the torch.

Beijing hopes such images of the torch's final passage through the host city will help banish memories of Tibet protests dogging the flame in Paris, London and elsewhere.

So police were quick to react to Wednesday's protest, taking 12 minutes to remove the group whom the official Chinese news agency Xinhua identified as Britons. A Chinese student group said the protesters also had U.S. participation.

"MAO WOULD BE HAPPY"

The Games have given China an unprecedented chance to showcase its modern face but have also galvanised critics of its human rights record. China's half-century rule in the Himalayan region of Tibet is the most contentious issue.

Demonstrations around the torch's international legs offended many Chinese, who see the Games as a moment of national pride for a nation some view as the emerging 21st century superpower.

"It's not just about the sport, it's about the image of China," said Xi Li, 29, one of thousands of officially organised well-wishers watching the torch near the entrance of the Forbidden City on the edge of Tiananmen Square.

"Chairman Mao would have been happy if he were here today!"

Unfortunately for organisers, the start of the flame's passage through Beijing took place under smog-filled skies.

Some $18 billion of cleanup measures have reduced contamination to safe levels, according to Olympics chiefs, but not produced the sunshine and blue skies China longs for.

Some anxious U.S. sportsmen arrived with face-masks on, though that drew disapproval from the International Olympic Committee (IOC) which said it was unnecessary.

Beijing has also spent a fortune on new buildings for the Games, including the extraordinary, steel-latticed Bird's Nest stadium that is the main venue.

And no money has been spared either on security. A 100,000-strong force is on hand in Beijing to deal with any terrorism threats or anti-government protests.

Authorities intensified security this week after suspected Muslim separatists attacked a group of jogging policemen with homemade explosives, killing 16, in the far west.

Several million visitors are pouring into China to watch the Games. Big names abound, with Roger Federer and Rafael Nadal, for example, bringing their long-running tennis rivalry to China.

Runners Usain Bolt, Asafa Powell and Tyson Gay are favourites to fight it out in the 100 metres men's race -- the highest-profile event for the title of Fastest Man on Earth.

On another international pressure-point for China, Team Darfur, a coalition of athletes seeking to draw attention to the conflict in Sudan, said Beijing had revoked the visa of its co-founder and Olympic gold medallist Joey Cheek.

Speedskater Cheek had planned to travel to China on Wednesday to support Team Darfur athletes. Beijing is a major investor in Sudan's oil industry and its largest weapons supplier.

Cheek called his visa denial "part of systemic effort by the Chinese government to coerce and threaten athletes who are speaking out on behalf of the innocent people of Darfur."

(Additional reporting by Chris Buckley)

(Writing by Andrew Cawthorne; Editing by Nick Macfie)

(For more stories visit our multimedia website "Road to Beijing" here; and see our blog at blogs.reuters.com/china)