China has seen a dramatic crackdown on civil liberties and freedoms since President Xi Jinping took power in 2012, with hundreds of human rights lawyers and activists detained or placed under monitoring in recent years.

Wang Quanzhang, a human rights lawyer detained for four-and-a-half years as part of a sweeping crackdown on human rights defenders, told AFP that police were blocking him and his wife from leaving their Beijing apartment unattended.

"They told us directly that there were two reasons, one was the US democracy summit, and they were also worried we would take part in World Human Rights Day," Wang, who was released last year, told AFP on Friday.

US President Joe Biden on Thursday held a virtual summit of more than 100 nations to discuss threats to democracy -- with China pointedly left off the guestlist.

Beijing police could not be reached for comment.

Xu Yan, a rights campaigner and the wife of imprisoned high-profile lawyer Yu Wensheng, posted on her verified Twitter account that a group of people had blocked her from opening her front door and said she would have to stay in until Friday night.

All Chinese activists invited to a European Union-organized Human Rights Day event Friday had also been blocked from attending in person.

The EU Delegation to China hit out at what it called "systematically violated" civil and political rights in the country in a statement Friday.

Pointing to a slew of issues including mass detention of minorities in Xinjiang as well as reported organ harvesting from detainees, the Delegation called for China to "thoroughly investigate" allegations and immediately release political prisoners.