Protests from Paris to San Francisco continue to overshadow the traditional world relay of the Olympic torch.

Presidential candidate Hillary Clinton, a US senator and former first lady, became the most prominent US politician to call for President George W Bush to boycott the opening ceremonies of the Beijing Games in August, citing China's crackdown in Tibet and other human-rights abuses.

Eighteen people were arrested in mass protests in Paris, where French officials were forced to extinguish the torch, cut short the public relay and transport the torch inside a bus for part of the journey through France, instead of letting an athlete carry the flame in the traditional fashion.

Police said that the torch was extinguished "for technical reasons" that were not related to the protests, but French media reported that the action was taken to protect the flame from the human-rights demonstrators lining the planned 28-kilometre route.

An International Olympic Committee (IOC) spokesman said that the group would not comment on the incidents.

"The torch is the responsibility of ... the local Olympic committee," he said, adding that the Olympic flame "never dies."

The first incident occurred about one hour after former world 400- metre-hurdles champion Stephane Diagana left the first level of the Eiffel Tower on the first leg of the torch's scheduled itinerary through the French capital.

After the demonstrations delayed the procession by at least two hours, the torch made the final leg of the trip by bus, shortening the route by at least one-fourth.

A number of scheduled ceremonies including one foreseen for the Chinese embassy were cancelled to avoid further incidents. Paris Mayor Bertrand Delanoe said that Chinese officials had cancelled a scheduled ceremony at City Hall.

Dozens of French lawmakers joined the anti-China protest, standing behind a Tibetan flag and a banner reading "Respect Human Rights in China," as the torch passed the seat of the National Assembly in central Paris, BFM television reported.

The disruptions occurred despite a heavy police presence following the torch's tumultuous passage Sunday through London, where at least 36 people were arrested.

Some 3,000 police officers were stationed on the ground, in the air and even on the Seine River, while the torch was accompanied by a security perimeter of some 400 police officers on foot, horseback, motorcycle and roller blades as well as in cars.

The media rights group Reporters Without Borders hung a large protest banner on the Eiffel Tower, and three of its members chained themselves to the monument.

Paris is the final European stop for the torch, which will then be flown to the western hemisphere for appearances Wednesday in San Francisco and Friday in Buenos Aires.

In the United States, police were bracing for numerous protests as the atmosphere worsened.

"At this time, and in light of recent events, I believe President Bush should not plan on attending the opening ceremonies in Beijing, absent major changes by the Chinese government," said Clinton, who is locked in a tight race with fellow Senator Barack Obama for the opposition Democratic presidential nomination.

Her call came as three protestors climbed San Francisco's famous Golden Gate Bridge and unfurled a Tibetan flag and banners proclaiming "One World One Dream" and "Free Tibet."

"We are part of the global independent movement for Tibet, and we are calling the world's attention to what's happening in Tibet right now," protestor Laurel Sutherlin told a local TV station as he dangled more than 50 meters above the bridge.

"China is trying to take this Olympic torch around the world and use it as an opportunity to become a global player. We are looking to unmask this propaganda and let the world know there's brutal oppression happening in Tibet."

Police had arrested four people on the bridge who appeared to be the support team for the cable climbers and took the three climbers into custody when they descended after two hours aloft.

Clinton faulted the Chinese for the violent clashes in Tibet and for "the failure of the Chinese government to use its full leverage with Sudan to stop the genocide in Darfur." She said that the Bush administration had been "wrong to downplay human rights in its policy towards China."

Bush has said he intends to participate in the opening ceremonies but will continue to press China on its human-rights record and to advocate open dialogue between Beijing and the exiled Tibetan spiritual leader, the Dalai Lama.

"We have a great deal of concern about human rights in China, ... and we have never been afraid to express those views either directly by the president or the president's senior advisers when they travel to China, and publicly," said Tony Fratto, a White House spokesman.

San Francisco police were readying for major protests along the only US stop for the Olympic torch relay. The route along the waterfront is designed to minimize potential disruptions by numerous protest groups.

The governing San Francisco Board of Supervisors called on the city to greet the Olympic torch with "alarm and protest."(dpa)