Chinese activist Hu Jia said he was beaten by men he identified as state security forces on Wednesday, the same day as a sensitive court case involving a firm founded by dissident artist Ai Weiwei.
Mr. Hu, a government critic and friend of Mr. Ai who was released from prison in June 2011 after completing a more than three-year sentence for subversion, said Chinese state security forces set on him to prevent him from leaving his flat.
"This is the first time it's happened since I left prison," he told AFP, adding he was bleeding and hurt after the incident on Wednesday evening, but did not require medical attention.
He said the men did not tell him why they were stopping him from leaving his home near Beijing.
Mr. Hu was jailed in 2008 after angering the ruling Communist Party through years of campaigning for civil rights, the environment and AIDS patients, and has been under surveillance since being released from prison.
The incident took place on the same day as a high-profile hearing in Beijing challenging a multi-million-dollar tax penalty brought against a firm founded by internationally-renowned Chinese artist Mr. Ai.
The case has been described by Mr. Ai as politically motivated, and it is hugely sensitive. Scores of police were outside the courthouse on Wednesday, telling foreign reporters to leave the premises. Mr. Ai himself was not allowed to attend.
Mr. Hu told AFP he had decided against going to court Wednesday after hearing Mr. Ai had not been allowed to go, and was set upon in the evening as he left his flat to buy groceries.
He said the altercation may have been linked to the sensitivity surrounding the tax case involving the firm Mr. Ai founded.
But he added the incident may also have been caused by a recent trip he took to Dongshigu village in eastern China to visit the relatives of blind activist Chen Guangcheng, who recently escaped house arrest and left for the United States.