China's foreign ministry described outgoing US secretary of state Mike Pompeo as a "doomsday clown" and said his designation of China as a perpetrator of genocide and crimes against humanity was merely "a piece of wastepaper".

The allegations of abuses against Muslim minority groups in China's Xinjiang region are "outright sensational pseudo-propositions and a malicious farce concocted by individual anti-China and anti-Communist forces represented by Pompeo", spokeswoman Hua Chunying told reporters at a daily briefing.

"In our view, Pompeo's so-called designation is a piece of wastepaper.

"This American politician, who is notorious for lying and deceiving, is turning himself into a doomsday clown and joke of the century with his last madness and lies of the century," Ms Hua said.

Mr Pompeo's announcement does not require any immediate actions, although the US must take the designation into account in formulating policy toward China.

China says its policies in Xinjiang aim only to promote economic growth and social stability.

The US has previously spoken out and taken action on Xinjiang, implementing a range of sanctions against senior Chinese Communist Party leaders and state-run enterprises that fund repressive policies in the vast, resource-rich region.

Last week, the Trump administration announced it would halt imports of cotton and tomatoes from Xinjiang, with Customs and Border Protection officials saying they would block products from there suspected of being produced with forced labour.

Many of the Chinese officials accused of having taken part in repression are already under US sanctions.

The "genocide" designation means new measures will be easier to impose.

Tuesday's move is the latest in a series of steps the outgoing Trump administration has taken to ramp up pressure on China over issues from human rights and the coronavirus pandemic to Taiwan, Tibet, Hong Kong and the South China Sea.

China has responded with its own sanctions and tough rhetoric.

China has imprisoned more than one million people, including Uighurs and other mostly Muslim ethnic groups, in a vast network of prison-like political indoctrination camps, according to US officials and human rights groups.

People have been subjected to torture, sterilisation and political indoctrination in addition to forced labour as part of an assimilation campaign in a region whose inhabitants are ethnically and culturally distinct from the Han Chinese majority.

Widespread forced birth control was reported among the Uighurs last year, including the mass sterilisation of Muslim women, even while family planning restrictions are loosened on members of China's dominant Han ethnic group.

China has denied all the charges, but Uighur forced labour has been linked by reporting to various products imported to the US, including clothing and electronic goods such as cameras and computer monitors.

James Leibold, a specialist in Chinese ethnic policy at La Trobe in Melbourne, Australia, said international pressure appears to have had some effect on Chinese policies in Xinjiang, particularly in prompting the government to release information about the camps and possibly reducing mass detentions.

"So hopefully we'll see a continued continuity with regards to the new (Joe Biden) administration on holding China to account," Mr Leibold said in an interview.

"And hopefully the Biden administration can bring its allies along to continue to put pressure on the Chinese government," he said.