Former security chief Zhou Yongkang under house arrest

China has put Zhou Yongkang, one of the most powerful politicians of the last decade, under virtual house arrest while the ruling Communist Party investigates accusations of corruption against him, several sources said on Wednesday.

Zhou is the most senior official to be ensnared in a graft scandal since the Communists came to power in 1949. He was the domestic security tsar and a member of the party’s Politburo Standing Committee – the pinnacle of power in the country – when he retired last year.

Chinese President Xi Jinping ordered a special task force formed in late November or early December to look into several accusations brought against Zhou by political rivals, sources with ties to the leadership said, requesting anonymity to avoid repercussions for discussing secretive elite politics.

“Zhou Yongkang’s freedom has been restricted. His movements have been monitored,” one source said, adding that he cannot leave his Beijing home or receive guests without prior approval.

Zhou is being investigated for violating party discipline, official jargon for corruption, the sources said. They did not say what the specific allegations were.

Xi was installed as head of the party just over a year ago, and as president in March, and the investigation illustrates his growing power and confidence that he can manage any rift that may ensue.