Updated

China said Thursday that 15 foreign ambassadors exceeded their diplomatic roles by issuing a letter expressing concern about the incarceration of hundreds of thousands of members of the country's Muslim minorities in re-education camps.

Foreign Ministry spokeswoman Hua Chunying told reporters at a daily briefing that it would be "problematic" if the diplomats were attempting to put pressure on local authorities in the northwestern region of Xinjiang, where the detentions have taken place.

Hua said the letter violated the terms of the Vienna Convention governing diplomatic relations and that the ambassadors should not "interfere in the internal affairs of other countries."

She said the letter was based on hearsay, despite widely distributed reports from detainees, relatives and officials documenting the sweeping and seemingly arbitrary detentions.

"As ambassadors, they are supposed to play positive roles in promoting mutual understanding, mutual trust and cooperation ... rather than making unreasonable requests to the countries where they are based," Hua said.

The letter issued this week was signed by 15 Western ambassadors, including the Canadian, British, French, Swiss, European Union, German, and Australian envoys, according to the Reuters news agency.

Hua's comments came as legislation is being brought by a bipartisan group of U.S. lawmakers who want President Donald Trump to help Chinese Muslims respond to the crackdown.

Xinjiang's native Uighur and Kazakh ethnic groups are culturally, religiously and linguistically distinct from China's Han majority and the region has been home to a low-intensity rebellion against rule from Beijing. Many of the region's natives say their culture is under threat from Chinese policies aiming to assimilate them and that they face disadvantages in education and employment from Han migrants from other parts of China.

Also on Thursday, China's Cabinet released a report entitled "Protection and Development of Xinjiang Culture," that stressed the importance of adopting Mandarin Chinese among ethnic groups and referred to their Islamic faith as "religious culture."

"Xinjiang adheres to the historical tradition of the Sinosization of religion and actively adapts religion to socialist society," the report said.