Chinese authorities are probing another senior figure for graft, officials said Tuesday, the latest politician with links to the country's former security chief to face investigation.

The Central Commission for Discipline Inspection (CCDI), the ruling Communist Party's much-feared internal watchdog, said on its website it is investigating Tan Li, the vice governor of the southern province of Hainan.

Tan is being probed for suspected "serious law and discipline violations", it said -- a euphemism for corruption.

Tan was previously the propaganda chief of Chengdu, the capital of the southwestern province of Sichuan -- one of the powerbases of Zhou Yongkang, the former security chief and Politburo Standing Committee (PSC) member who is at the centre of rumours about a corruption probe.

If the investigation into Zhou is confirmed, it would mark the first time in decades that such a high-ranking figure has been targeted in a formal inquiry.

Zhou's fall would send shockwaves through China's political establishment, as PSC members have generally been regarded as untouchable even after retirement.

Two weeks ago, authorities stripped three senior allies of Zhou of their Communist Party membership -- Jiang Jiemin, the former head of China's state-owned assets watchdog; Li Dongsheng, former vice minister of public security; and Wang Yongchun, a former top official at China National Petroleum Corp (CNPC).

They were the latest of more than a dozen officials to be targeted in the sweeping probe into Zhou, who has not been mentioned by name in state-run media reports.