China has a long history of accusing the US of fomenting anti-China separatism in Xinjiang. (File)

China on Thursday accused the United States of seeking to "disturb" its security policies after a US congressional report said Beijing's mass internment of Muslim minorities may constitute "crimes against humanity".

The report by the Congressional-Executive Commission on China described the situation of human rights in China as "dire" and worsening, a trend epitomised by the internment of as many as one million Uighurs and other ethnic minorities in the far west Xinjiang region.

In response, China's foreign ministry characterised reports of its policies in the region as "rumours and groundless accusations".

Chinese policies "aim to safeguard the social stability and security of Xinjiang and are supported by the people," foreign ministry spokesman Lu Kang told reporters during a regular press briefing.

"Relevant parties want to disturb such efforts. This is futile," he said.

Beijing has a long history of accusing the US of fomenting anti-China "separatism" in Xinjiang, alleging Washington has sponsored groups advocating for the region's independence in an attempt to weaken China.

The region -- which comprises one-sixth of China's land area -- is a jumping off point for the country's ambitious new "Belt and Road" project aimed at opening up new overland routes to increase access to markets across Asia and Europe.

Maintaining stability there has become a priority for the country's leadership, which seeks to prevent any disruptions to its economic ambitions.

Beijing has long had a strained relationship with Xinjiang's mostly Muslim minority groups, particularly the Turkic Uighurs, which make up about half of the region's population and bridle under the central government's draconian security policies.

The region experienced a brief increase in attacks following deadly riots in the regional capital Urumqi in 2009.

Beijing says its policies towards the region have effectively eliminated the problem.

But critics say that the measures are unsustainable and will stoke resentment as China seeks to assimilate Xinjiang's minority population and suppress religious and cultural practises that conflict with Communist ideology and the dominant Han culture.

China has sought to achieve that goal by detaining hundreds of thousands in a network of shadowy "re-education" centres where they are force-fed propaganda and drilled on Chinese language skills, according to rights groups.

Beijing has denied the existence of the centres, while admitting that some people accused of minor crimes have been put in correctional programmes where they receive job training.

But on Tuesday, Xinjiang updated its counter-terrorism and anti-extremism regulations to codify such centres, saying that people accused of minor crimes related to terrorism would be allowed to voluntarily enter the facilities instead of being jailed.

But there may be little difference between the two.

In July, a former teacher at one of the centres told a court in Kazakhstan that "in China they call it a political camp but really it was a prison in the mountains."