Two senior Chinese politicians seen as allies of disgraced former security czar Zhou Yongkang were formally charged with corruption offences on Thursday, officials said.

Jiang Jiemin and Li Chuncheng were both accused of bribery and abuse of power, China's top prosecutor said on its website.

Jiang is the former head of the body that regulates China's state-owned firms, while Li was a senior Communist Party official in the southwestern province of Sichuan.

The trials, which will take place at an at unspecified date, will pave the way for a court appearance by Zhou, the most senior official to fall in an anti-corruption crackdown overseen by Chinese President Xi Jinping.

Jiang is a former head of the China National Petroleum Corporation, a post previously held by Zhou, and the two are reportedly part of a Communist Party faction with roots in the oil industry, known as the "petroleum gang".

Li is also seen as a close associate of Zhou, once a member of China's all-powerful Politburo Standing Committee who amassed vast power as head of China's internal security apparatus.

In December Zhou was arrested, ousted from the party and placed under a judicial probe on charges including bribe-taking and "leaking state secrets".

Communist Party authorities have waged a much-publicised campaign against endemic graft since Xi ascended to the organisation's leadership two years ago.

But critics say no systemic reforms have been introduced to increase transparency and help battle the problem, while anti-corruption demonstrators have been jailed.

Corruption trials of former officials in China are closely managed by the ruling party, which retains control of China's police, prosecution and courts.