CHINA - Talk that China's retired security czar Zhou Yongkang is in trouble has been going around since his rumoured ally Bo Xilai's political downfall last year.
Now news that Beijing has approved a probe into Mr Zhou - which will make him the most senior official to be investigated for economic crimes - coupled with recent arrests of people close to him, will spook officials more than the just-ended trial of Bo, a former Politburo member.
Mr Zhou, 70, retired from the apex Politburo Standing Committee (PSC) - one rung higher than the Politburo - last November. He had spent his career in the state oil industry and wielded power as head of domestic security.
Some see the probe as a signal by Beijing that it is serious about fighting corruption.
"Zhou Yongkang is facing a more determined and stronger leader Xi Jinping, who has great resolve and is determined to push for anti-corruption. (Xi) correctly realises that this is about the survival of the Communist Party," said Professor Huang Jing of the Lee Kuan Yew School of Public Policy.
Professor Xiao Bin, an anti-corruption expert from the Sun Yat-sen University in Guangzhou, said the arrest of "tigers" like Mr Zhou will send a strong message of deterrence.
Other observers said it remains to be seen if Beijing will eventually press criminal charges against Mr Zhou, who is said to be close to retired top leader Jiang Zemin and to enjoy support in the massive public security apparatus.
Prosecuting him would also break a "mutual protection clause" that keeps past and present members of the PSC, China's top decision-making body, immune from criminal prosecution, said Hong Kong analyst Willy Lam.