Families of lawyers and rights activists detained by China's Communist authorities exactly a year ago urged authorities to stop harassing them on Saturday, as they repeated calls for the release of their relatives.

More than 200 attorneys and rights campaigners were held in a huge operation launched on July 9, 2015 known as the 709 crackdown -- named after the date of the first disappearance.

"We strongly demand the Chinese government to release all the detainees involved in the 709 crackdown... Stop all the monitoring, harassment, shadowing and persecution towards all the detainees' families," the relatives said in a statement sent to AFP.

They added that they were tightly monitored by the police on a "24-hour basis".

"We are tailed, force(d) to move out of our house, harassed at midnight, obstructed from work and there are children who can hardly enter a school. We can no longer continue our normal life," they said.

In total, 23 lawyers and rights activists held during the 709 crackdown are still in detention, according to the document's signatories, all but one of whom are the wives of the detainees. The other is a sister.

"Over the past year... our efforts were always in vain as we were greeted by the officials with indifferences and rejections."

Under President Xi Jinping, who came to power in 2012, China has tightened controls on civil society, and the 709 crackdown represents its largest-scale operation in years.

On Monday, five spouses of the detained men donned dresses emblazoned with their husbands' names and marched to a national prosecutors' office in Beijing -- surrounded by dozens of police.

The UN High Commissioner for Human Rights described the detentions as "worrying", but Beijing routinely dismisses such complaints as interference in its internal affairs.