The report came shortly before high-ranking diplomat Rahm Emanuel, the US ambassador to Japan, stated on social media that Li "hasn't been seen or heard from in 3 weeks," and that the minister might have been placed under house arrest.

It is the latest sign of potential turmoil in Beijing after Chinese foreign minister Qin Gang inexplicably disappeared and was ousted from his post in July.

China also replaced the leadership of its Rocket Force, the army unit that oversees its nuclear arsenal, in July, with its former commander Li Yuchao not seen in public for weeks before the change and official media Xinhua giving no explanation for his removal.

Asked by AFP on Friday whether Li Shangfu was under investigation, a Chinese foreign ministry spokeswoman said she was "not aware of the situation you raise."

The Times reported that three US officials as well as two people briefed on intelligence said the United States determined Li Shangfu had been stripped of his duties as minister.

It was not clear what made President Joe Biden's administration conclude that Li was under investigation. The White House has not publicly addressed the matter.

Li traveled to Russia in August to attend a security conference near Moscow on August 15. Two days later, the government of Belarus released handout photographs of Li meeting with Belarusian President Alexander Lukashenko in Minsk.

Li has refused to hold meetings with US counterparts until Washington lifts sanctions on him, imposed by then-president Donald Trump in 2018 for his procurement of Russian military technology.

The latest apparent removal of an elite Chinese official from public view led Ambassador Emanuel, who has been openly critical of Chinese President Xi Jinping, to fuel speculation about the issue on September 7 and again one week later.

"President Xi's cabinet lineup is now resembling Agatha Christie's novel And Then There Were None. First, Foreign Minister Qin Gang goes missing, then the Rocket Force commanders go missing, and now Defense Minister Li Shangfu hasn't been seen in public for two weeks," Emanuel posted last week on X, the former Twitter, using the hashtag #MysteryInBeijingBuilding.

On Thursday, in another post on his official ambassador account that appeared to openly provoke the Xi government, he questioned whether Beijing authorities have restricted Li's movements.

"1st: Defense Minister Li Shangfu hasn't been seen or heard from in 3 weeks. 2nd: He was a no-show for his trip to Vietnam," he wrote.

"Now: He's absent from his scheduled meeting with the Singaporean Chief of Navy because he was placed on house arrest???... Might be getting crowded in there."

Emanuel is a former White House chief of staff who earned a reputation in Washington for his ferocious style and hardball politics.

The remarks come at a time of heightened trade and geopolitical tensions between Washington and Beijing.