China warned a bipartisan group of U.S. lawmakers not to interfere in its internal affairs Thursday after they sought sanctions against Chinese officials over allegations the country was holding as many as 1 million Muslims in “reeducation” camps.

The 17 legislators—led by Senator Marco Rubio of Florida and Representative Chris Smith of New Jersey—requested the penalties Wednesday in a letter addressed to Secretary of State Michael Pompeo and Treasury Secretary Steven Mnuchin. They want to unleash the Global Magnitsky Act of 2016, which has been employed to punish Russian oligarchs and Turkish officials, to restrict the travel and freeze the assets of top Communist Party officials.

“The policies and equal rights that Chinese minorities enjoy are far better than in the U.S., which has lot issues with racism and human rights protection,” Chinese Foreign Ministry spokeswoman Hua Chunying told a briefing in Beijing. The lawmakers should focus on issues at home “instead of interfering in other countries’ internal politics, playing judges on human rights and casting blame, or even threatening to impose unreasonable sanctions,” she said.

The proposal, which had been previously floated by at least one State Department official, represents the most serious response yet to reports of the camps in its western region of Xinjiang. The bid underscores the potential for ties to deteriorate further as Trump pressures Chinese counterpart Xi Jinping over trade and blames the dispute for derailing nuclear talks with North Korea.

“There have been recent reports of deaths in custody, including suicides, in Xinjiang, and the Chinese government shows no signs of halting these rights violations,” the lawmakers said. “At a time when the Chinese government is seeking to expand its influence through the Belt and Road Initiative, the last thing China’s leaders want is international condemnation of their poor and abusive treatment of ethnic and religious minorities.”

The lawmakers specifically called for sanctions against Xinjiang’s regional party secretary Chen Quanguo, a member of China’s 25-member Politburo who has helped create one of the world’s most restrictive security regimes after a series of attacks in 2013 and 2014. The Alaska-sized area has become a land of checkpoints, police stations and security cameras, where residents must install satellite tracking systems in their cars and submit to facial scans to enter markets, buy fuel or visit bus terminals.

Scrutiny of China’s practices in the region has increased since a United Nations official earlier this month described as “credible” reports that Xinjiang authorities had jailed roughly 10 percent of its ethnic Uighur minority. China has dismissed the allegations, saying “anti-China forces have made unwarranted charges against China for political purposes.”

The Magnitsky Act, which imposes sanctions on officials accused of human rights violations, is named for the Russian lawyer and whistleblower Sergei Magnitsky who died in a Moscow prison in 2009. While it’s unclear what effect such measures would have against Chinese officials whose overseas movement and wealth transfers already face internal restrictions, sanctions would represent an embarrassing diplomatic blow to Xi.

State Department spokeswoman Heather Nauert declined to comment on the letter at a briefing Wednesday, saying she had not seen it. “It’s certainly something that we would—we would take a look at and consider, however,” Nauert said.

The Trump administration has recently shown an willingness to use the legislation against Turkish officials in his dispute over the detention of an American pastor. Acting Deputy Assistant Secretary of State Laura Stone told reporters in April that China’s actions against the Uighur minority made it a potential target for Magnitsky Act sanctions.