China will retaliate "in proportion" if the United States sanctions its top official in its far-west Xinjiang region over alleged human rights abuses, China's ambassador to the US said, adding Beijing's policies there are to "re-educate terrorists".
Chinese Ambassador Cui Tiankai compared actions in Xinjiang with US troops battling the Islamic State of Iraq and the Levant (ISIL, also known as ISIS), and told Reuters news agency that China's efforts to combat international terrorism were held to a double standard.
"Can you imagine [if] some American officials in charge of the fight against ISIS would be sanctioned?" Cui said, adding "if such actions are taken we have to retaliate".
Cui did not elaborate on specific actions China might take.
Beijing has faced an outcry from activists, academics, foreign governments and the United Nations over mass detentions and strict surveillance of the Uighur minority and other Muslim groups in Xinjiang.
In August, a UN human rights panel said it had received many credible reports that one million or more Uighurs were being held in what resembles a "massive internment camp that is shrouded in secrecy".
US officials have said the Trump administration is considering sanctions targeting companies and officials linked to China's crackdown on minority Muslims, including Xinjiang Party Secretary Chen Quanguo, who is a member of the powerful politburo and in the upper echelons of China's leadership.
Cui said while the United States was using missiles and drones to kill terrorists, "we are trying to re-educate most of them, trying to turn them into normal persons [who] can go back to normal life".
"We'll see what will happen. We will do everything in proportion," he said, responding to a question on how China would retaliate to possible US sanctions on Chen.
Cui's comments are the strongest response yet to US threats on the issue.
Any decision by the US to impose sanctions on such a senior official as Chen would be a rare move on human rights grounds by the United States, which is engaged in a trade war with China but also wants Beijing's help to resolve a standoff over North Korea's nuclear weapons.
US sanctions could be imposed under the Global Magnitsky Act, a federal law that allows the US government to target human rights violators around the world with freezes on any US assets, US travel bans, and prohibitions on Americans doing business with them.
Chinese authorities deny any ethnic or religious repression in Xinjiang. They say strict security measures - likened by critics to near martial law conditions, with police checkpoints, detention centres, and mass DNA collection - are needed to combat the influence of "extremist" groups.
After initial blanket denials of the detention facilities, officials have said some citizens guilty of "minor offences" were sent to vocational centres to improve employment opportunities.
At a briefing in Washington on Monday, a Uighur woman, Mihrigul Tursun, 29, told reporters she experienced physical and psychological torture, including electrocution while strapped to a chair, during 10 months in detention in Xinjiang.
Rejecting Chinese government claims that the detention facilities serve vocational purposes, she said many of the dozens of other women in her cell were "well-educated professionals, such as teachers and doctors".
China's embassy in Washington did not immediately respond to a request for comment on Tursun's statement.
Independent assessments of the conditions in Xinjiang are nearly impossible given restrictions on journalists from openly reporting from the region.
UN human rights chief Michelle Bachelet has called on China to allow monitors in Xinjiang, but Beijing has responded by telling her to respect China's sovereignty.