Citing current and former US officials familiar with the situation, British newspaper the Financial Times said the investigation into Dong was part of that broader probe into military corruption.

If confirmed, Dong would be the third Chinese defence minister in a row to fall under investigation for corruption.

Asked about the report at a regular briefing on Wednesday, Chinese foreign ministry spokewoman Mao Ning said it was just "chasing shadows" and did not offer further information.

A former navy commander, he was appointed defence minister in December following the surprise removal of predecessor Li Shangfu just seven months into the job.

Li was later expelled from the ruling Communist Party for offences including suspected bribery, state media said. He has not been seen in public since.

His predecessor, Wei Fenghe, was also kicked out of the party and passed on to prosecutors over alleged corruption.

"It's certainly a blow... because one would imagine they will be super careful to have someone very clean in this role," Dylan Loh, an assistant professor at Singapore's Nanyang Technological University, told AFP.

"Graft probes are very commonly targeted at the military because of the long historical ties between the business world and the PLA," he said, referring to the Chinese military by its official acronym.

- Deepening crackdown -

Beijing has deepened a crackdown on alleged graft in the armed forces over the past year, with President Xi Jinping this month ordering the military to stamp out corruption and strengthen its "war-preparedness".

The intensity of the anti-graft drive in the army has been partially driven by fears that it may affect China's ability to wage a future war, Bloomberg reported citing US officials this year.

"If the corruption probe into Dong Jun is true, then it is normal that people will question if it will erode morale and if it will affect the PLA's warfighting capabilities," Nanyang Technological University's Loh said.

The country's secretive Rocket Force -- which oversees China's vast arsenal of strategic missiles, both conventional and nuclear -- has come under particularly intense scrutiny.

In July, a top Chinese official in the Rocket Force, Sun Jinming, was placed under investigation for corruption.

Sun was kicked out of the ruling Communist Party and placed under investigation for "grave violations of party discipline and laws", state news agency Xinhua said at the time, using a common euphemism for graft.

At least two other high-ranking officers connected to the Rocket Force, a relatively new unit of the Chinese military, have also been removed for graft.

Victor Shih, an expert on China's elite politics, told AFP that Dong "likely had authority over tens of billions in procurement per year" during his time in the navy.

"The problem is that competition for top positions is so fierce that there might be some mutual recriminations between officers, which would lead to endless cycles of arrests, new appointments and recriminations," he said.

Benjamin Ho from the China programme at Singapore's S. Rajaratnam School of International Studies told AFP there were "a couple of possibilities" for the reported investigation.

"One is the vetting process is wrong, or the other is that there is some kind of political scandal or problem out there which in this case somehow Dong Jun had to take the fall for."