The official Xinhua News Agency said in a brief announcement that Zhou Yongkang's position as head of the Political and Legal Affairs Committee, a sprawling body that oversees law-and-order policy, had been taken over by Public Security Minister Meng Jianzhu.
The hulking, grim-faced 69-year-old Zhou had to retire along with most members of the Politburo Standing Committee, the inner council at the apex of power, at this month's 18th Party Congress, due to his age. He turns 70 in December.
Meng, however, is only a member of the new Politburo, the 25-member body which reports to the down-sized Standing Committee, putting him on a tighter leash and returning to a pattern the party kept to for much of the 1980s.
Reducing the party's Standing Committee from nine to seven members came as part of a once-in-a-decade leadership change announced last week, which saw Vice President Xi Jinping raised to head of the ruling Communist Party.
Reuters reported in August that Zhou's position was likely to be downgraded and Zhou replaced by Meng.
Zhou had been on the Standing Committee since 2007 while also heading the central Political and Legal Affairs Committee.
That double status allowed Zhou to dominate a domestic security budget of US$110 billion a year, exceeding the defense budget.
Zhou was implicated in rumors that he hesitated in moving against the politician Bo Xilai, a former candidate for top office who fell in a divisive scandal after his wife was accused of murdering a British businessman.
Security forces also suffered a humiliating failure earlier in the year when they allowed blind rights advocate Chen Guangcheng to escape from 19 months of house arrest and flee to the U.S. Embassy in Beijing.
Since the 1990s, China's efforts to stifle crime, unrest and dissent have allowed the domestic security apparatus — including police, armed militia and state security officers — to accumulate power.
In another announcement, Xinhua said that Zhao Leji had replaced Li Yuanchao as head of the party's organization department that oversees the appointment of senior party, government, military and state-owned enterprise officials.
Zhao had been party boss of the northern province of Shaanxi and is close to president-in-waiting Xi.
There was no announcement on where Li, a reformer who has courted foreign investment and studied in the United States, may go. He missed out on a spot on the Standing Committee despite being tipped to enter it.
Standing Committee positions will officially be released in March at the annual meeting of parliament, though there is no doubt Xi will become president and Li Keqiang will take over as premier from Wen Jiabao.
Over the next few days and weeks state media should announce the positions of the other members of the Politburo.