China's disgraced former domestic security chief, Zhou Yongkang, looks set to be expelled from the ruling Communist Party at a key meeting next week, sources said, possibly paving the way for his formal prosecution.

Zhou is the most senior party member to have been targeted in a corruption probe since the Communists swept to power in 1949, and President Xi Jinping has made fighting graft a cornerstone of his administration.

At a four-day party plenum beginning on Monday in Beijing, the Central Commission for Discipline Inspection, its main anti-graft body, will present its findings in a report on Zhou, said three sources, who all spoke on condition of anonymity.