GENEVA (Reuters) - Bar associations from nearly 20 countries called on Chinese President Xi Jinping on Monday to release Wang Quanzhang, saying that the lawyer has been held incommunicado for more than three years with his legal rights denied.

FILE PHOTO: Li Wenzu, wife of lawyer Wang Quanzhang, who was detained in what is known as the "709" crackdown, joins others protesting in front of the Supreme People's Procuratorate in Beijing, China July 7, 2017. REUTERS/Damir Sagolj

Wang, who took on sensitive cases of complaints of police torture and defended practitioners of the banned Falun Gong spiritual movement, went missing in August, 2015 during a sweeping crackdown on activists.

“At the time of writing, he has been held incommunicado for over three years without any form of due process, and risks further deterioration of his health condition while in detention,” said the petition letter to Xi issued on the 70th anniversary of the Universal Declaration of Human Rights at the initiative of the Geneva Bar Association.

“We are profoundly concerned about lawyer Wang, and all the other lawyers who face continuous harassment simply for the exercise of their mandate as legal professional and defenders of the basic rights of citizens,” it said.

Chinese authorities launched what rights groups say was a coordinated attempt to quash China’s rights movement in what is known as the “709” crackdown.

Charged in January, 2016 with alleged “subversion of state power”, Wang is the only one of 321 lawyers and activists arrested in that crackdown who has yet to be tried or released, the letter said.

“We understand that no evidence of any form or shape has substantiated the charges put against him,” it said.

“Wang Quanzhang was not given access to an independent legal counselor of his choosing and has been denied access to his family lawyer, who was allegedly intimidated into withdrawing from his case,” said the letter, whose other signatories include the New York City Bar, the Swedish Bar Association, The Law Society of England & Wales, and the China Human Rights Lawyers Concern Group.

Wang’s wife Li Wenzu has filed 30 lawsuits demanding a trial for her husband, in line with Chinese law, it said, adding that she and their son have been harassed and denied the right to visit Wang. Li set off this year on a march of more than 100 kilometers from Beijing to Tianjin city where she believes her husband is being held.

China rejects foreign criticism of its human rights record and points to its successes in pulling millions of people out of poverty as proof of human rights progress in the country.