The US has called for Chinese authorities to allow a prominent human rights lawyer to return home, after having spent almost five years in “unjust detention”.

Wang Quanzhang was released two weeks ago after serving four-and-a-half years for “subversion”, but told Hong Kong’s Cable TV on Monday that the authorities were still stopping him from returning home and being reunited with his family.

On his release, Wang was sent for two weeks of compulsory coronavirus quarantine to his home town of Jinan, instead of to Beijing, where he lives with his wife and seven-year-old son. At the end of the 14 days his wife, Li Wenzu, said Wang was still being barred from returning to Beijing, and was under strict supervision.

“I am most desperate to be reunited with my wife and son. Now Jinan [police] seem to want to restrict me from returning to Beijing,” said Wang, who added that there is no legal basis for holding him in his home town but he was “trying his best” to persuade the authorities to allow him home.

The US state department said: “We remain very concerned about reports of his declining physical and mental health, and of his mistreatment in prison.

“Wang was detained as part of the PRC’s [People’s Republic of China] nationwide roundup of more than 300 human rights lawyers and legal associates beginning 9 July 2015.

“We continue to call for the release of all of those unjustly detained, such as Li Yuhan and Yu Wensheng, as well as other Chinese citizens who are in detention simply for exercising their human rights and fundamental freedoms in pursuit of a more equitable and just society, governed by the rule of law.”

In his interview on Monday – the first time Wang has been heard publicly for five years – he confirmed speculation he had been detained the longest of all those caught up in the 2015 crackdown because he refused to confess.

“I never confessed, I would not compromise my principles,” he said, adding that the authorities kept putting pressure on him between 2016 and 2018 to confess.

“I have no regrets,” he said. “I don’t think I have anything to boast about. I’m not some sort of hero … I do what I am meant do as a lawyer.”

When the Guardian attempted to contact him, a male voice answered the call, saying he was not Wang. It appeared that Wang was back under police supervision.

His wife told the Guardian she could not go to Jinan because the authorities would likely put the whole family under strict surveillance for up to two years, as has happened to many human rights lawyers after their release from prison.

“We have been apart for five years and I’ve been anxious for five years. He needs a free environment and to be reunited with our son, to make up for all these years when he wasn’t around,” she said.

The US statement also expressed continued concern over China’s “weak rule of law”, arbitrary detention and torture of detainees, and human rights violations.

The practice of releasing activists from prison into de facto house arrest or to their home town has been labelled “non-release release” by rights groups.

Human Rights Watch’s China researcher, Yaqiu Wang, said the Chinese government seemed determined to silence Wang indefinitely, and called his continued detention “a complete travesty of justice”.