Two influential former Chinese leaders gave their consent for President Xi Jinping to investigate ex-domestic security chief Zhou Yongkang, sources told Reuters, a sign the corruption probe will not open a rift in the ruling Communist Party.

Xi would not have been able to investigate someone as powerful as Zhou without the agreement of senior party members and other retired top officials, political analysts said.

But less clear is whether the elite is starting to get jittery over Xi's expanding corruption crackdown, which is spreading fear throughout the party and the government.