Men who appeared to be plainclothes security agents separated the two sides and led the protesters away, said Jw where the protesters were taken.
Officials at the Beijing Public Security Bureau and Tiananmen Square police station would not comment.
Tethong identified Saturday's activists as Chris Schwartz of Montreal, Canada; Diane Gatterdam, Evan Silverman and Joan Roney from New York; and David Demes of Germany.
Earlier this week, Students for a Free Tibet held similar small protests, where they displayed Tibetan flags and hung pro-Tibet banners near the National Stadium, a key Olympics venue. Seven have been deported to Europe and the United States.
Over a half hour after the protest, Tiananmen Square appeared normal. Hundreds of tourists were at the famous tourist site.
Visitors are required to put their bags through security scanners before entering the square, scene of the 1989 pro-democracy student protests. Groups of guards stood under large umbrellas about every 50 feet, but they appeared relaxed.
Tibet has been an extremely sensitive topic since protests against almost 50 years of Chinese rule turned violent in the region's capital of Lhasa in March.
Many Tibetans insist they were an independent nation before Communist troops invaded in 1950, while Beijing says the Himalayan region has been part of its territory for centuries.
Pro-Tibet activists say China is using the sporting event to legitimize its rule in Tibet.