GENEVA (Reuters) - A Chinese lawyer held for more than 16 months without trial is being unlawfully detained for his human rights work and should be released, a United Nations watchdog has said.

The U.N. working group on arbitrary detention issued its opinion on Yu Wensheng, dated May 29, after examining his case at a closed-door meeting of its five independent experts.

There was no immediate comment by China.

It is the 30th anniversary on Tuesday of a bloody crackdown on pro-democracy protesters in and around Beijing’s Tiananmen Square.

Yu had been the defense attorney of jailed prominent rights lawyer Wang Quanzhang before being stripped of his license and then arrested outside his home in January 2018. He is still under investigation for “inciting subversion”.

“The Working Group concludes that the deprivation of liberty of Mr. Yu resulted from the peaceful exercise of his rights to freedom of expression and of association and his right to take part in government, and was contrary to article 7 of the Universal Declaration of Human Rights. His deprivation of liberty is arbitrary,” the experts said.

Yu should be released immediately and provided compensation in line with international law, they said.

The Chinese government missed the deadline to submit its response, including to allegations that Yu has been denied any visits with a lawyer of his or his family’s choosing during his entire detention, the experts said.

Yu, now 51, was sent to Xuzhou City Detention Center in Jiangsu Province, where police placed him under “residential surveillance”, they said, adding that this amounted to incommunicado and secret detention.

He has been charged with “a vague and imprecise offense of inciting subversion of State power”, they said.

“This provision does not define what conduct amounts to subversion and overthrowing the socialist system through rumors, slander or other means. The communication of mere thoughts, ideas or opinions could potentially fall within the prohibited conduct,” the U.N. body said.

Yu had worked peacefully within China’s legal system and nothing suggested he had engaged in or incited violence, it said.