?This photo taken on February 1, 2006 shows China’s former security chief Zhou Yongkang (center) visiting grass root police officers in Guiyang, southwest China’s Guizhou province. — AFP ?

BEIJING — China’s ruling Communist Party announced an investigation into a feared ex-security chief on Tuesday, underlining President Xi Jinping’s firm grip on power and breaking a longstanding taboo against publicly targeting the country’s topmost leaders. The party’s anti-graft watchdog, the Central Commission for Discipline Inspection, said on its website that it is investigating Zhou Yongkang for serious violations of party discipline, but gave no details. Such an announcement typically paves the way for the official to be ousted from the party and face prosecution. Until his retirement in 2012, Zhou was one of nine leaders in the party’s ruling inner circle — the Politburo Standing Committee — whose incumbent and retired members had been considered off-limits for prosecution in recent decades in an unwritten rule aimed at preserving party unity. However, party leader and President Xi has vowed to target both low- and high-level officials in his campaign to purge the party of corruption and other wrongdoing that has undermined its legitimacy in the public eye. — AP