(CNN) A prominent human rights activist and China critic based in Kazakhstan, has been arrested by Kazakh police and charged with inciting ethnic strife, according to his lawyer.

Serikzhan Bilash is the co-founder of Atajurt, an Almaty-based organization that brings attention to the crackdown on Muslims in China's western region of Xinjiang.

Aiman Umarova, Bilash's lawyer, said that her client was arrested on Saturday night in Almaty and transferred to Astana, the Kazakhstan capital. Umarova added that Bilash was "roughed up" during his arrest.

If convicted, he could face up to 10 years in prison.

Kazakhstan authorities could not be reached for comment.

According to the US State Department, citing reports from international rights groups, scholars, and media organizations, as many as 800,000 to 1.1 million individuals have been detained in camps in Xinjiang since around April 2017.

Bilash and other critics argue the facilities are re-education camps for political indoctrination and are an attempt to erase any Islamic presence from the region under a so-called policy of sinicization -- a process that attempts to assimilate minority cultures into the majority Han Chinese culture.

Muslim minorities

Atajurt has publicly lobbied for the closure of the Xinjiang camps and published accounts of those who had been detained and released.

The group's YouTube channel is populated by stories of people in Kazakhstan who say their family members are missing in Xinjiang, locked in camps and unable to leave.

Though the vast majority of those detained are Uyghur, the State Department says ethnic Kazakhs and other Muslim minorities living in China have also been detained.

Over the past year, Bilash has repeatedly told CNN about what he called an ongoing campaign of harassment by the Kazakhstan authorities.

Bilash says Astana has failed to oppose the camps because of the billions of dollars of investment Beijing has poured into Kazakhstan infrastructure projects in recent years, as part of its Belt and Road Initiative.

Centers 'essentially boarding schools'

The arrest comes as Xinjiang's most senior Uyghur official, chairman Shohrat Zakir, defended the detention centers on the sidelines of a meeting of China's National People's Congress in Beijing Tuesday.

Zakir reiterated the Chinese government's long-held stance that the camps are "vocational training centers" where residents are taught voluntarily as part of an anti-radicalization program.

"Claims that the trainees are abused and their freedom is restricted in the centers are wrong. The centers are essentially boarding schools. And food and lodging are all free," Zakir said at an open session of Xinjiang's delegates to the Congress.

The official added that the centers had been "effective" in stopping religious extremism in Xinjiang, claiming the facilities protected detainees' dignity and human rights.

Zakir denied there were more than a million people in the camps, and said as more Uyghurs "graduated" from the Xinjiang centers the number of inmates would decrease.

"Generally speaking, there will be fewer and fewer trainees in these vocational training centers. If one day, the society doesn't need them anymore, vocational training centers will disappear gradually," he said.