BEIJING — 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.

A Foreign Ministry spokeswoman, Hua Chunying, told reporters at a daily briefing that it would be “problematic” if the diplomats were trying 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.”

“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.

She said the letter issued this week and reportedly spearheaded by Canada was based on hearsay, despite widely distributed reports from detainees, relatives and officials documenting the sweeping and seemingly arbitrary detentions.

Inmates and relatives say the camps impose military-style discipline and punishments and force detainees to renounce their religion and culture while swearing fealty to President Xi Jinping and the ruling Communist Party.

Asked about the letter, Canadian Prime Minister Justin Trudeau said he had “highlighted the questions and concerns that we have” surrounding the issue in his bilateral meeting with Chinese Premier Li Keqiang on the sidelines of the annual summit of the Association of Southeast Asian Nations in Singapore.

“Canada will continue to look for ways to advance and promote human rights in partnership with our likeminded allies everywhere around the world,” Trudeau said at a news conference Thursday.

The letter to the Chinese government has not been made public, but the Reuters news agency said it was signed by 15 Western ambassadors, including the Canadian, British, French, Swiss, European Union, German, and Australian envoys.

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