Protests over China's crackdown on Tibet forced organisers in Paris to put the Olympic torch on a bus on Monday to protect it from demonstrators.
A police source said the torch was placed aboard a bus shortly after setting off from the Eiffel Tower.
A member of the French Greens party had earlier been restrained by police when trying to grab the torch from the first of 80 torch bearers, former world 400 metres hurdles champion Stephane Diagana.
Escorted by security, Diagana was wearing a badge reading "For a better world", an initiative decided by the athletes' commission of the French Olympic committee.
Several hundred demonstrators waving banners gathered on the Trocadero esplanade, just the other side of the river Seine from the Eiffel Tower, where the relay got under way at 1035 GMT.
France has deployed more than 3,000 police officers, some on roller blades, along the 28-km Paris leg of relay, to the Charlety stadium, on the southern edge of town, where the torch was due to arrive at 1500 GMT.
"Boycott Chinese goods" and "Save Tibet" read some of the banners held by the demonstrators, watched by police in riot gear and prevented by barriers from getting near the course.
"We are doing our best but it will take the world to put pressure on China to help bring democracy and human rights to Tibet," said Phurbu Dolker, a 21-year-old Tibetan refugee.
Thousands of protesters waving Tibetan flags and shouting "Shame on China" tried to disrupt the torch's run through London on Sunday, the British leg of the international relay billed by Beijing as the "harmonious journey".
French human rights minister, Rama Yade, denied on Saturday that President Nicolas Sarkozy would boycott the Games' opening ceremony unless China started talks with the Tibetan spiritual leader, the Dalai Lama, and released political prisoners.
The Olympic flame is expected to remain a magnet for anti-Chinese protests ahead of the August Games in Beijing.
The flame is due to return to Beijing on Aug. 6, two days before it will be used to light the cauldron at the Olympic opening ceremony.
