The Chinese dissident Chen Guangcheng is reported to have fled to the American embassy in Beijing following a dramatic escape from house arrest.
Fellow activist Hu Jia has told the BBC that Mr Chen, who is blind, scaled a high wall and was driven hundreds of kilometres to Beijing.
Activists say Mr Chen escaped about five days ago and has since released a video addressed to Prime Minister Wen Jiabao.
The US state department has refused to comment on the claim that Mr Chen is in its embassy and the US embassy in Beijing has also not commented.
There are reports Mr Chen's brother and nephew are being held by police.
Mr Chen had been under house arrest since his release from jail in 2010.
His reported escape comes days before China and the United States hold high-level talks in Beijing.
Bob Fu, an American-based rights campaigner and friend of Mr Chen, says activists offered the dissident safe passage out of China but he refused.
"The only thing he told me was that he wants to fight to the end for freedom and basic rights inside China - for himself, his family and for others. So he chose to stay in China ... he wants to make his voice heard in the international community and to the Chinese leaders."