BEIJING  Armed with her laptop and her indignation, Zhu Xiaomeng sits in her dorm room here, stoking a popular backlash against Western support for Tibet that has unnerved foreign investors and Western diplomats and, increasingly, the ruling Communist Party.

Over the last week, Ms. Zhu and her classmates have been channeling anger over anti-China protests during the tumultuous Olympic torch relay into a boycott campaign against French companies, blamed for their country’s support of pro-Tibetan agitators. Some have also called for a boycott against American chains like McDonald’s and Kentucky Fried Chicken.

On Friday and Saturday, protesters gathered in front of a half-dozen outlets of the French retailer Carrefour, including a demonstration in the central city of Wuhan that reportedly drew several thousand people, according to Agence France-Presse. On Saturday, about 50 demonstrators carrying banners held a brief rally at the French Embassy here before the police shooed them away.

For the moment, however, most of the outrage is confined to the Internet. More than 20 million people have signed online petitions saying they plan to stop shopping at the Carrefour chain, Louis Vuitton and other stores linked to France because of what they see as the country’s failure to protect the torch during its visit to Paris two weeks ago. In a survey released on Friday, China’s state news agency, known as Xinhua, said 66 percent of those who responded said they would stay away from Carrefour during a monthlong boycott planned for May.