China on Tuesday accused one of its former top military officers of taking "huge" bribes for promotions, as President Xi Jinping presses home a campaign against graft in the country's vast defense establishment.

Guo Boxiong, 74, was a vice chairman of the powerful Central Military Commission until he stepped down in 2012. The government announced a corruption investigation into Guo last July.

In a terse statement on the Defence Ministry's website, the military said it had handed Guo over for prosecution after investigators completed their probe into him.

"Guo Boxiong used his position to provide help for others in promotions or reassignments, and took a massive amount of bribes either directly or via his family," it said in the statement, which was also carried by the Xinhua official news agency.

"Guo Boxiong confessed everything."

Investigators collected a mass of evidence against him but also ensured he had access to a lawyer and read and signed off on all the transcripts of his questioning, Xinhua added.

Sources had previously told Reuters that Guo might not face prosecution as he has cancer.

His case follows that of Xu Caihou, who was also a Central Military Commission vice chairman at the same time as Guo, and died of bladder cancer in March last year. The government said in 2014 that Xu had also confessed to taking "massive" bribes in exchange for help in promotions.

Before their retirement, the men had been two of China's top military officers who served together under Xi's predecessor, Hu Jintao. Xi was also a vice chairman with Guo and Xu from 2010 to 2012, before he became party head and military commission chief.

Guo's son, Guo Zhenggang, who is a major-general, was put under investigation in March last year.

It was not possible to reach either Guo for comment and it was not clear who their lawyers are.

Xinhua said family members and others implicated in the case would also be dealt with by the law, though it gave no details.

Guo Boxiong was a "greedy degenerate" who would get what was coming to him, the defense ministry said in an online commentary.

For over a decade, Guo sat on the Central Military Commission, in charge of the world's largest armed force, numbering around 2.3 million, after joining the army in 1961 and rising through its ranks, according to his official biography.

In 2006 he visited the United States and met then-defense secretary Donald Rumsfeld.

Serving and retired military officers have said graft in the armed forces is so pervasive it could undermine China's ability to wage war. Xi has made weeding out corruption in the military a top goal.

The drive comes as Xi steps up efforts to modernize forces that are projecting power across the disputed waters of the East and South China Seas, though China has not fought a war in decades.

China intensified its crackdown on military corruption in the late 1990s, banning the People's Liberation Army from business. But recent years have seen the military involved in commercial deals, due to a lack of checks and balances, military analysts have said.