Dong's promotion comes at a sensitive time, as Beijing ups military pressure on the self-ruled island of Taiwan ahead of presidential elections next month and grows increasingly assertive in disputed waters in the South China Sea.

His predecessor Li Shangfu was ousted after seven months in the role following a lengthy absence from public view -- one in a series of recent high-level disappearances from the country's military establishment and political class.

In July, foreign minister Qin Gang was removed from office after disappearing from the public eye for a month.

Both Qin and former defence minister Li were believed by experts to have been personally selected for their roles by President Xi Jinping.

Beijing has not given an official reason for either man's removal.

Fighting alleged corruption has been a central theme of Xi's rule, which has been punctuated by high-level removals and disappearances of officials.

Recent months have also seen an overhaul in the leadership of China's secretive Rocket Force, the army unit that oversees Beijing's nuclear arsenal, following media reports of a graft probe involving its former chief

And three executives at leading Chinese missile defence firms were removed from Beijing's top political advisory committee this week, according to state media.

- Surprise promotion -

Dong was appointed at a meeting of the standing committee of China's National People's Congress, state news agency Xinhua said.

Dong, born in 1961, was made commander of the navy in August 2021.

He was replaced by Hu Zhongming earlier this month.

Dong previously served as deputy commander of the Chinese military's Southern Theater Command, which includes as its area of operation the South China Sea, where Beijing has territorial disputes with neighbouring countries.

Dong's appointment "is a sign of China seeing South China Sea as a new priority area of geopolitical contestation between China and the US", Wen-Ti Sung, a political scientist at Australian National University, said in a post on social media platform X.

It "also follows existing tradition of appointing non-Army generals to lead China's military diplomacy", he added.

His promotion comes as a surprise, however.

Many analysts had expected Liu Zhenli, a 59-year-old general and head of China's joint staff department, to become the new defence minister.

He notably spoke last week with his American counterpart during the first high-level call between military personnel from the two leading world powers in more than a year.

That followed an agreement by President Joe Biden and Xi at a summit last month to restore military communications between their two countries, which China severed after then US House speaker Nancy Pelosi visited Taiwan in 2022.

Biden at the time said the move was "critically important" to avoid possible conflicts.

But that summit also saw Xi warn the US president against supplying further arms to Taiwan, insisting China's reunification with the island was "unstoppable".