The nephew of blind Chinese lawyer Chen Guangcheng was jailed for more than three years for attacking officials who descended on his village after the dissident fled to the US embassy, his father said.

Chen Guangcheng, who was imprisoned after exposing abuses under China's "one child" population control policy, caused a diplomatic row when he escaped house arrest in his village in Shandong province and reached the US mission in Beijing.

As he was freed to leave for the United States, government officials and police descended on his village home, prompting his nephew Chen Kegui to attack them with a kitchen knife, wounding three people.

"He was sentenced to three years and three months, this is extremely unfair. There is no principle in Chinese law, I feel there is no hope," Chen Guangfu, Chen Kegui's father, told AFP by phone from outside the courthouse.

"From what I understand, Chen Kegui will not appeal the sentence. They refused to allow me in to observe the trial, so there are a lot of details that I still don't know about."

Chen Kegui appeared thin but in good health at the trial on Friday, his father said, adding that another relative was allowed to observe the proceedings and sent news of the verdict to the family.

Court officials were not immediately available to confirm the verdict and sentence, which came after a three and a half hour trial. He had been charged with the crime of intentional injury.

The United States blasted the Chinese authorities for jailing Chen Kegui, saying he was the victim of a "deeply flawed legal process".

"We are deeply disturbed about reports that Chen Kegui... was tried and convicted today in a legal proceeding in China that lacked basic due process guarantees," State Department spokeswoman Victoria Nuland told reporters.

"He was convicted in a summary trial in which he was not fully represented by legal counsel of his choosing. He didn't have an opportunity to present his own defense. So this was a deeply flawed legal process."

The family has maintained that authorities barged into their home in the middle of the night unannounced and uninvited, and refused to identify themselves when the attack took place.

One of China's best-known activists, Chen Guangcheng won plaudits for investigating rights abuses including forced sterilisations and late-term abortions under China's "one-child" family planning policy.

After being released from a four-year jail term in September 2010, Chen was put under house arrest in Shandong but fled from under the noses of plain-clothes police on April 22.

He took refuge at the US embassy in Beijing less than a week before US Secretary of State Hillary Clinton was due to visit China for high-level talks.

Chinese and American diplomats scrambled to find a solution to defuse the row. After initially agreeing to stay in China, Chen decided he wanted to leave for the US and Beijing eventually agreed to allow him to apply to study abroad.

Chen Kegui has been in police custody since April 26, with local officials refusing visits, dismissing lawyers hired by the family and appointing government attorneys.

The court-appointed lawyers informed the family of Friday's trial only hours before it started, making it impossible for the lawyers they had hired to reach the courthouse in time for the trial, Chen Guangfu said.

"The lawyers are a part of the same gang (the government), they were useless, I don't know any details of their defence for him (Chen Kegui)," he added.

Nicholas Bequelin of Human Rights Watch commented on Twitter: "Chen Kegui's trial failed to meet minimum standards of fair trial under domestic or international standards."