Runners carried the Olympic torch through the streets of San Francisco on Wednesday, but on a truncated path more than a kilometre away from thousands of pro-Tibet and pro-China demonstrators who had lined the expected relay route.

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A Tibetan supporter, right, argues with a Chinese supporter at a rally for China's Olympic torch at the Ferry Plaza in San Francisco. ((Jeff Chiu/Associated Press))

Flanked by a massive police motorcade and officers brandishing batons, the torch was brought to two runners waiting at an unannounced location, a move that effectively thwarted both protesters and eager spectators.

The crowds along the previously announced route included many people waving Chinese flags in support of China and the Beijing Games ahead of the run along the city's waterfront, which was originally scheduled to start at 1 p.m. PT in its only North American stop.

But just minutes before it was to begin, San Francisco police told spectators that the 10-kilometre relay route would be several kilometres shorter than originally planned.

Then in a bizarre scene at the planned starting point, the torch disappeared into a warehouse as IOC officials and torch runners, surrounded by police, huddled to discuss alternate plans with city authorities.

A few minutes later, television cameras showed a number of people dressed in official Beijing 2008 track suits boarding a convoy of buses, which then drove out the back entrance of the warehouse complex with a police motorcycle escort.

San Francisco Mayor Gavin Newsom had said the route could change minutes before or during the relay.

Less than an hour before the relay began, officials cut the original 10-kilometre route nearly in half.

The planned closing ceremony at the San Francisco Bay waterfront was cancelled and moved to San Francisco International Airport on Wednesday evening. The flame was put directly onto a plane and not displayed.

Crowds of more than 10,000 spectators and protesters had gathered at the waterfront when news reached them that the location was no longer on the torch's route.

Rival sides face off

The rival protest groups were given side-by-side permits to demonstrate, and there already were signs of tension and reports of minor scuffles and shouting matches, the CBC's Laurie Graham reported. One pro-Tibet activist was detained ahead of the run, according to Reuters.

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Chinese swimmer Lin Li waves the Olympic torch on Wednesday during the torch relay in San Francisco. ((Paul Sakuma/Associated Press))

"A lot of Tibetan people are getting killed," said Kunga Yeshi, 18, who had travelled to San Francisco from Salt Lake City, Utah. "The Chinese said they'd change if they got the Olympics, but they still won't change."

Across the street, a bus carrying dozens of pro-China supporters arrived.

"The Olympic spirit unites all human beings, not only Chinese — also America and the whole world," said Hui Chen, 36, of San Jose.

One torchbearer showed her support for Tibetan independence by pulling out a small Tibetan flag hidden in her shirt sleeve when she was handed the Olympic flame

"The Chinese security and cops were on me like white on rice, it was no joke," said Majora Carter, 41, who runs a nonprofit organization in New York. "They pulled me out of the race, and then San Francisco police officers pushed me back into the crowd on the side of the street."

Security was tightened for the afternoon run along the city's waterfront in the wake of demonstrations in London and violent protests in Paris.

But beefed-up security didn't prevent the disruptions during the Paris segment of the relay, which had to be suspended at least five times as demonstrators threatened the torch. A vehicle carried the Olympic flame for the last part of the route, but a runner was allowed to carry the torch for the final five metres into a sports stadium in the south of Paris.

On Sunday, police repeatedly scuffled with protesters in London, including one who tried to grab the torch, while another tried to snuff out the flame with what appeared to be a fire extinguisher.

On Monday, three pro-Tibet activists climbed the suspension cables of the Golden Gate Bridge to protest arrival of the torch relay.

The protesters unfurled two giant banners reading "One World, One Dream" and "Free Tibet '08" — a play on the official slogan of the Beijing Games. One of the climbers also displayed a Tibetan flag.

B.C. student taken off bridge

The climbers, and four people who helped them, were arrested and charged with trespassing, conspiracy and causing a nuisance. One of the four helpers was Ali Taub, a Canadian student who attends the University of British Columbia.

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Olympic torch bearer Dean Karnazes, 44, of San Francisco participates in a media event on Tuesday in San Francisco. ((San Francisco Chronicle/Kim Komenich/Associated Press) )

Taub told CBC News police were on scene within two minutes of their protest and she was taken off the bridge soon after.

"Some of the police walked me through as the banners went up and said 'one world, one dream, free Tibet' and they were really excited so I heard via [police] it went really well," she said.

Taub said the charges have been dropped and that a lot of the police force was supportive of the protest.

After San Francisco, the torch is scheduled to travel to Buenos Aires and then to a dozen other countries. It will enter mainland China on May 4 for the host country's portion of the relay.

In an interview with the Wall Street Journal, International Olympic Committee president Jacques Rogge said there are no plans to cut the relay short but that the issue will be discussed during a board meeting in Beijing on Friday.

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Kalsang Gyaltsen, foreground, chants during a pro-Tibet rally on Tuesday in San Francisco. ((Noah Berger/Associated Press) )

IOC vice-president Kevin Gosper echoed his remarks, saying the relay will go ahead as planned.

"We won't scrap the torch relay," he said. "We'll keep up the torch relay. We [must not] step back.

"We're very disturbed and disappointed that there are people who want to disrupt the process. We understand peaceful protests. We understand that in many democracies. But we don't condone people who want to disrupt and be violent and run the risk of injury."

With files from the Associated Press