Fourth top aide of ex-security tsar Zhou Yongkang probed after being 'snatched by authorities'

A former secretary of ex-security tsar Zhou Yongkang is reportedly under investigation, joining three other occupants of the role who are already being probed for graft.

Shen Dingcheng, the party chief and vice-president of PetroChina International, disappeared shortly before the Lunar New Year holiday, the China Business Journal reported, citing an anonymous source.

Shen is among an extensive network of Zhou's allies who have been snatched by the authorities.

They range from the Beijing city spy chief Liang Ke to Sichuan mining tycoon Liu Han , who is accused of running a massive mafia ring.

The China Business Journal, which like other publications did not mention Zhou by name, said Shen became a secretary to "a particular leader at China National Petroleum Corporation [CNPC] at some point between 1992 and 1997". Zhou held the positions of deputy manager and general manager of CNPC at that time.

The report also highlighted Shen's links with three other former secretaries to Zhou and even described Shen as being part of a "gang of four" secretaries.