Following the Communist Party of China Central Committee's announcement that former security chief Zhou Yongkang is being investigated on suspicion of "serious disciplinary violations”, PetroChina Co Ltd led a rally of oil stocks in morning trading on Wednesday.

Shares in the country's biggest oil and natural-gas producer by output rose 3.33 percent to 8.06 yuan a share at the close of morning trading in Shanghai. Sinopec Ltd, the biggest oil refiner, gained 1.16 percent to 5.23 yuan a share.

Zhou, a former member of the Politburo Standing Committee, China's top decision-making body, started his political career at PetroChina and is widely thought to have acolytes throughout the country’s oil industry.

Twenty of the 21 oil-related companies in both the Shanghai and Shenzhen bourses rose, amid a 0.13 percent drop in the benchmark Shanghai Composite Index, ending a six-day rally.

Caging corrupt 'tigers'	Infographic: Zhou's associates who were probed