Gao Zhen, 70, and his brother Gao Qiang gained fame in the early 2000s for art touching on sensitive political topics such as the Cultural Revolution, the Tiananmen Square protests and the legacy of Mao, who led China from 1949 until his death in 1976.

Their works include a sculpture of the Communist leader kneeling, titled "Mao's Guilt", and another called "Execution of Christ", in which several bronze statues of Mao aim rifles at a statue of Jesus.

Gao Zhen, who moved to the United States in 2022, was detained at his studio on the outskirts of Beijing during a visit to China in August 2024.

The artist -- whose name can also be written as Gao Shen -- was indicted in June last year on charges of "insulting... heroes and martyrs", according to the US-based group Chinese Human Rights Defenders (CHRD).

CHRD told AFP on Tuesday Gao was sentenced to three years in prison -- the maximum sentence for that crime -- at Sanhe City Court in northern Hebei province.

Chinese authorities appeared to be applying a 2021 law retroactively to works that Gao created between 2005 and 2009.

The United Nations' high commissioner for human rights called for Gao to be "immediately and unconditionally released".

"The case against him raises particular concerns with regard to the retroactive application of criminal law, the use of criminal sanctions to punish artistic expression, and the impact on his family," the Office of the High Commissioner for Human Rights said in a statement sent to AFP.

According to rights groups, Gao's wife and their son, a US citizen, have been banned from leaving China since 2024.

"That's a human rights violation on its face, collective punishment extending to his family," CHRD's Shane Yi told AFP.

Giving Gao the maximum prison term showed the determination of Chinese authorities "to deter others from engaging in independent artistic expression", said Sarah Brooks, China director for rights group Amnesty International.

"No artist should face criminal punishment for creating work that challenges official narratives or encourages critical reflection on history," Brooks said in a statement.

According to Amnesty, Gao is due to complete his sentence next August, but has decided to appeal against both the prison term and his conviction.

Multiple calls to the court by AFP on Tuesday went unanswered.

AFP has also contacted the US State Department for comment.