A Chinese campaigner under constant surveillance today told how activists have been detained, put under house arrest or driven out of Beijing in a last-minute clampdown before the Olympic opening ceremony tomorrow.

Zhang Xianling lives on the very edge of the Olympic Village, but is being watched round the clock by police officers who have based themselves in her apartment complex. She said the move is a last-ditch measure to prevent protests during the Games.

The long-time human rights defender, who invited the Evening Standard into her home despite being monitored, said she wanted the world to "know the truth" about China.

Her invitation came as President Bush expressed "deep concerns" about China's human rights record, just hours before he flew to Beijing for the Games.

Mrs Zhang said: "It's completely unjust to monitor us and make us prisoners in our own home.

"It's illegal, we are not under house arrest, we are just watched and have a constant presence outside our house."

The 71-year-old retired engineer has been targeted by the authorities for founding the campaign group Tiananmen Mothers, after her son Wang Nan was killed aged 19 in the Tiananmen Square massacre which followed a pro-democracy demonstration in June 1989.

Since its foundation the group has been calling for the release of those still imprisoned and for a full and public accounting for the shootings.

Mrs Zhang and her husband Wang Fan Di, a 75-year-old retired music professor, have had two police officers outside their home, just minutes from the city's Birds Nest stadium, every day for the past week.

She added that a fellow founding member of Tiananmen Mothers, Ding Zilin, a Nobel peace prize nominee, has been removed from her home in Beijing by police officers, who escorted her out of the city. She is temporarily staying in the city of Dalian, 300 miles away.

"At first I was completely against China hosting the Olympics but now I am glad the whole world is watching," said Mrs Zhang, who has been detained in the past. "The buildings and the roads are all new and clean but the human rights situation has not changed. Not even these Olympics will change that."

Mrs Zhang's niece, a teacher from West Hampstead, said: "The Chinese government is using the Olympics to showcase their Communist regime." The 52-year-old, who as a member of the banned religion Falun Gong can never return to China, added: "We want a real Olympics, a harmonious one. Under the current regime this will not happen. The human rights situation is the worst it's ever been."

International concern over the human rights record of the regime is set to grow after Mr Bush's outspoken intervention, which will send shockwaves through the Chinese Communist leadership. "The US believes the people of China deserve the fundamental liberty that is the natural right of all human beings," he said in the Thai capital, Bangkok.

"America stands in firm opposition to China's detention of political dissidents, human rights advocates and religious activists.

"We speak out for a free press, freedom of assembly and labour rights - not to antagonise China's leaders but because trusting its people with greater freedom is the only way for China to develop its full potential.

"And we press for openness and justice not to impose our beliefs but to allow the Chinese people to express theirs."