Chinese defence minister Li Shangfu abruptly pulled out of a meeting with Vietnamese defence leaders last week, three officials with direct knowledge of the matter said, amid questions about his more than two-weeks-long absence from public view.

Li, 65, was due to attend an annual gathering on defence cooperation hosted by Vietnam on its border with China on Sept. 7-8 but the meeting was postponed after Beijing told Hanoi days before the event that the minister had a "health condition," two Vietnamese officials said.

The sudden postponement of the meeting and the reasons cited by China are being reported by Reuters for the first time.

China's State Council Information Office, as well as its defence and foreign ministries did not immediately respond to a request for comment about the Vietnam event. The Vietnamese embassy in Beijing couldn't immediately be reached for comment Thursday evening.

The abrupt cancellation of Li's trip follows China's unexplained replacement of Foreign Minister Qin Gang in July after a prolonged absence from public view and a shake-up of the leadership of the People's Liberation Army's elite Rocket Force in recent months, moves that have raised questions about the Chinese leadership's decision-making.

Qin's meteoric ascent through the ranks of the Communist Party was partly attributed to his closeness to President Xi Jinping, making his removal after just seven months on the job even more unexpected. Chinese officials initially said Qin's absence from public view was due to health reasons.

Li was appointed to his post in March. He is watched closely by diplomats and other observers because, like Qin, he is also one of China's five State Councillors, a cabinet position that ranks higher than a regular minister.

A U.S. official, on condition of anonymity, said Washington was aware of Li's cancelled meetings with the Vietnamese. U.S. President Joe Biden visited Hanoi last week, where the two sides inked a historic upgrade of their partnership.

Li's prolonged absence from public view has drawn some comment. U.S. Ambassador to Japan Rahm Emanuel posted on X, formerly Twitter, on Sept. 8: "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. Who's going to win this unemployment race? China's youth or Xi's cabinet?"

Asked about Emanuel's post this week, a Chinese Foreign Ministry spokeswoman told reporters she was "not aware of the situation."

Li was last seen in Beijing on Aug. 29 delivering a key-note address at a security forum with African nations. Before that he held high-level meetings during a trip to Russia and Belarus.

China's defence minister is mainly responsible for defence diplomacy and does not command combat forces. He has a less public profile than the foreign minister, who frequently appears in state media.

"Li's disappearance, following so shortly after Qin, speaks to how mysterious Chinese elite politics can be to the outside world," said Alfred Wu, associate professor at the Lee Kuan Yew School of Public Policy in Singapore.

"China under Xi simply does not feel a need to explain itself to the world."

Li was sanctioned by the U.S. in 2018 for buying weapons from Russia's largest arms exporter, Rosoboronexport.

Chinese officials have repeatedly said they want those sanctions dropped to facilitate better discussions between the two sides' militaries. U.S. Defence Secretary Lloyd Austin attempted talks with Li during a defence conference in Singapore in June, but did not get beyond a handshake.

In 2016, Li was named deputy commander of the military's then-new Strategic Support Force - an elite body tasked with accelerating the development of space and cyber warfare capabilities. He then headed the military's procurement unit from 2017 until he became defence minister.

In a rare notice in July, the unit said it was looking to "clean-up" its bidding process and invited the public to report irregularities dating back to 2017. There has been no update on possible findings.