The brother of a blind activist who has fled China said he himself was savagely beaten by two men on Thursday, in what he called an intensification of reprisals against the activist's family.

Chen Guangfu said his family has endured a campaign of harassment beginning last month, ahead of the first anniversary of the escape of his brother Chen Guangcheng from house arrest to seek asylum at the US mission in Beijing.

The flight provoked talks to avert a diplomatic crisis which ended with Chen taking up residence in the US. But the lawyer's family has reported retaliation from local authorities ever since.

In the latest incident Chen Guangfu told AFP that two young men emerged from a black vehicle and grabbed him, kicking and punching him "in a very professional style" before driving away.

"Before, we were just being harassed, now there are physical attacks... the situation has become more serious," said Chen, 56, adding: "I am very worried for my whole family's safety."

It was not clear who the men were but Chen said they did not appear to be from the area where the family lives, near Dongshigu in the eastern province of Shandong.

Chen Guangfu's son Chen Kegui was sentenced to three years in prison last year in what supporters allege was retribution by authorities for his uncle's escape.

He is suffering from acute appendicitis but has been denied medical parole, Chen said. Rocks and dead poultry have been thrown at his family's house in recent weeks, he added.

Chen Guangcheng had run afoul of authorities in Shandong by exposing forced abortions and sterilisations under China's one-child policy. He was jailed and later reported severe beatings while under house arrest.

Chen Guangcheng, who currently lives in New York, has said that a number of attacks against his family members have occurred since mid-April, according to the US-based advocacy group China Aid.

Local police in Linyi close to Dongshigu said they were dealing with Chen's case and refused further comment on Thursday.