Then secretary of the Central Secretariat of the Communist Party of China Ling Jihua attends the plenary session of the Chinese People's Political Consultative Conference at the Great Hall of the People on March 8, 2013 in Beijing, China.[Photo/CFP]

Zhou was reported to have formed several networks within the fields he was in charge of, including central and local governments, law enforcement organs and State-owned enterprises, such as China National Petroleum Corp, where a number of corrupt officials investigated for involvement in Zhou's case have been dubbed the "oil clique", according to the Xinhua report.

Zhou has been expelled from the Party and transferred to the Supreme People's Procuratorate for further investigation and trial.

Ling, a senior Party official and national political adviser who is the latest state leader to come under investigation, has aroused attention from media at home and abroad.

Ling has established a secretive network known as the "Shanxi clique" with other high-ranking officials and business managers from his home province of Shanxi to expand his influence, Xinhua reported.