Chinese police on Saturday detained five members of groups supporting independence for Tibet after they staged a "die-in" in Beijing Tiananmen Square, the London-based Free Tibet Campaign said in a statement.
Four of the protesters wrapped themselves in Tibetan flags and lay down on the square to stage a "mock die-in" while the fifth protesters explained to onlookers that they were "calling for an end to the Chinese government's occupation of Tibet", the statement said.
Police took them away about 10 minutes later, it said.
The protesters reportedly included three US citizens, one German and one Canadian, reported dpa.
"The Chinese government is seeking to cover up its ugly occupation of Tibet with the bright lights of the Olympics," Matt Whitticase of the Free Tibet Campaign said in the statement.
"Our action at Tiananmen Square today highlights the determination of Tibetans and people of conscience that no amount of repression from the Chinese government will extinguish the desire of Tibetans for freedom and to speak out against China's worsening abuses in Tibet," Whitticase said.
"The Chinese government will not be allowed to use the Olympics to hide the reality of its harsh rule inside Tibet," said Lhadon Tethong, Executive Director of Students for a Free Tibet.
Despite the heavy security in Beijing, foreign activists have managed to stage other protests in recent days.
Two US and two British citizens were detained on Wednesday after the Britons scaled a 40-metre lighting post near the Olympic Green and unfurled a huge banner calling for independence for China's Tibet region.
The Free Tibet Campaign said three more protesters were detained one hour before the opening ceremony on Friday, after they displayed Tibetan flags near the Olympic Green.
All seven people involved in the two earlier protests were quickly deported from China, the group said.
Three US anti-abortion campaigners also staged a brief sit-in on the edge of Tiananmen Square on Wednesday afternoon, state media said.