Zhang Wei and Ma Xiulan, who have been vocal about the pain of losing their traditional family compounds near Tiananmen Square, were rounded up late on Wednesday and early on Thursday morning, according to Ma.
The efforts are part of stringent security measures for the games by Chinese communist authorities determined that the Olympics should be an international showcase for the country.
With the world's eyes turned on Beijing in anticipation of the games, which start on Friday, activists have stepped up their protests to publicize their causes.
The groups so far have been small and police have acted with relative restraint. No arrests have been reported, although the Beijing Olympics organizing committee has condemned the demonstrations.
Ma said officers came to her door at 2 a.m. and bruised her arm while grabbing her. Reached by the AP on her cell phone, she said she was at a local police station with Zhang and a number of other residents but could not give any other details.
"The police are watching me and are restricting my phone use," Ma said. "They are not letting me talk to reporters, especially the foreign media. I'm here because I talked to the foreign media before."
She then quickly hung up the phone.
A woman who answered Zhang's cell phone said Zhang had been taken away a little before midnight by two police officers and one plainclothes security agent. She refused to give her name for fear of official retribution and would only say she was a family member.
Two officers who answered the telephone at the police station where Ma said she was being held said no one had been detained and refused to give any more information because they were not authorized to speak to the media.
Qianmen, the historic area where the homes of Zhang and Ma were located, is south of Tiananmen Square and has undergone a huge makeover to make way for a commercial strip housing businesses such as Nike, Starbucks and Rolex.
Thousands of people have been forced from courtyard homes that have been passed down for generations to make way for the redevelopment, part of larger relocations throughout Beijing as a property boom transforms the city's landscape.
Earlier this week, some 20 people angry about their evictions from Qianmen demonstrated near Tiananmen Square in a rare protest around the tightly guarded area. The demonstrators scuffled with neighborhood officials as police watched.
Also Thursday, a second protest by three Americans in Tiananmen Square was stopped by security agents, including at least one plainclothes police officer, who blocked the group from view with umbrellas before grabbing their arms and leading them away.
A day earlier, the trio, including anti-abortion activist Rev. Patrick Mahoney, spent almost an hour in the square criticizing the government's handling of issues ranging from forced abortions to the banned Falun Gong spiritual movement to pro-democracy demonstrations in 1989. They also unfurled a banner that said "Christ is King."
Another group of foreigners, pro-Tibet activists, were detained Wednesday after climbing up lamp poles outside the Beijing National Stadium, also known as the Bird's Nest, and putting up banners proclaiming "Free Tibet."
Two of the four detained activists from Students for a Free Tibet - both of them British - were deported to Frankfurt, Germany, group spokesman Matt Whitticase said Thursday.
Two others, US citizens, were still in custody, Whitticase said.
Foreigners who protest Beijing's human rights record or official policy of atheism on Chinese soil normally face deportation. Chinese who demonstrate face detention and hours of questioning by police, at the very least.
The government also has used its visa rules to try to keep out foreigners who might want to protest. Former Olympic speedskater and Darfur campaigner Joey Cheek had his visa pulled on Wednesday, hours before he was to travel to Beijing.
