The Chinese Foreign Ministry has said it has no knowledge that US diplomats were being subjected to “undignified” anal probing in order to test for Covid-19 in China, refuting reports published by Vice on Wednesday.

“To my knowledge… China has never required US diplomatic staff stationed in China to conduct anal swab tests,” Foreign Ministry spokesman Zhao Lijian told a daily press briefing on Thursday.

Zhao’s comments come after US news outlet Vice cited a US State Department spokesperson on Wednesday who said that Washington had protested directly to the Chinese Ministry of Foreign Affairs after hearing that American diplomatic staff had been subjected to anal swab testing.

Washington complained that the practice was “undignified” and Beijing responded, claiming the tests were given “in error” and promised that diplomatic personnel would be exempt from the practice, the spokesman told Vice.

“We have instructed staff to decline this test if it is asked of them, as was done in the past,” the spokesman added.

It is unclear how many American diplomats and their families were subjected to the practice.