BEIJING (AP) — China’s ruling Communist Party announced an investigation into a feared ex-security chief on Tuesday, demonstrating 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, 71, 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, the square-jawed, granite-faced 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 an unwritten rule aimed at preserving party unity.
However, Xi, who is party leader as well as president, has vowed to target both low- and high-level officials in his campaign to purge the party of corruption and other wrongdoing that have undermined its legitimacy in the public eye.
If he goes to trial, Zhou would be the highest-level official to prosecuted since the 1981 treason trial of Mao Zedong’s wife and other members of the ‘‘Gang of Four,’’ who mercilessly persecuted political opponents during the chaotic 1966-76 Cultural Revolution.
By targeting Zhou, who had commanded China’s massive domestic security apparatus before his retirement, Xi shows the considerable power he has amassed since he took the helm of the party in November 2012.
Tuesday’s announcement was a ‘‘powerful demonstration’’ that Xi and his graft-fighting right-hand man, fellow Standing Committee member Wang Qishan, are ‘‘really in control,’’ said Ding Xueliang, an expert on Chinese politics at the Hong Kong University of Science and Technology.
‘‘This is a huge, huge success for them. It is really remarkable,’’ Ding said. ‘‘For the broadly defined party state system, which has many millions of members, now they have to face the new reality. That is: You are not immune to punishment.’’
Li Datong, a political commentator who has been removed from a state media senior editing job for broaching sensitive subjects, said Xi means to show that ‘‘if he’s willing to go after a person like Zhou Yongkang, then there’s no one he won’t be willing to take on.’’
Although retired, Zhou still had threatened to interfere with Xi’s political agenda in order to protect his own personal interests, Li said. ‘‘Zhou was a rival who couldn’t be entirely controlled.’’
By dismantling Zhou’s spheres of influence, Xi also has freed up important positions in strategic areas of the government, security apparatus and state enterprises that he can fill with his own allies.
The announcement ended months of speculation over Zhou’s fate that had built up as several high-ranking officials and businesspeople and dozens of other known associates came under investigation, amid reports of Zhou’s family amassing great wealth. One after another, the associates disappeared into the custody of party investigators, foreshadowing problems ahead for Zhou.
Also Tuesday, the Chinese news magazine Caijing reported that Zhou’s son had been arrested by prosecutors in the city of Yichang in Hubei province, accused of ‘‘illegal business operations.’’
Zhou himself was last seen in October and is believed to have been detained sometime thereafter, although there has been no public announcement.
Zhou was once perceived as untouchable, with expansive patronage networks covering the sprawling southwestern province of Sichuan where he was once party boss, the state oil sector, and the police and courts.
More significantly, as China’s security chief, he oversaw the country’s domestic spy agencies, a position that afforded him access to information on other high-ranking politicians who might pose a threat to him.
If not for his spectacular downfall, Zhou’s life could have been an inspirational rags-to-riches tale. He was born the son of an eel fisherman in a little-known eastern village, the eldest of three boys and the only one to attend university, from which he graduated as an engineer, according to influential financial news magazine Caixin.
Zhou spent the early part of his career in the oil sector, rising through the ranks over several decades to become the general manager of China National Petroleum Corp., one of the world’s biggest energy companies, in 1996. He then served as party chief of Sichuan province between 1999 and 2002. He became a Politburo Standing Committee member and the national security chief in 2007.
In order to launch an investigation into Zhou, Xi would likely have had to overcome opposition from high-level party officials and retired leaders concerned about how it would hurt the party’s image. By breaking the unwritten rule of not targeting leaders of that level, the move also raises questions of whether more top leaders will be implicated.
‘‘No doubt, there must have been huge resistance’’ within the party leadership, said Zhang Lifan, an independent expert in Beijing on elite Chinese politics. Refering to Xi’s pledge to target senior officials, nicknamed ‘‘tigers,’’ in the crackdown, Zhang said, ‘‘today, the side that is striking out at the tigers has won the momentum.’’
Zhang said the party’s reference to ‘‘disciplinary violations’’ in its investigation of Zhou could refer to allegations that his family used his influence and position to seek benefits for themselves. Zhang said that now the case has come to light, the party leadership could not afford to appear weak or it would risk reprisals from those who opposed the move.
‘‘One thing is for sure, that is the tiger must be beaten to death, otherwise those who attack tigers will lose their sense of security,’’ Zhang said.
Xi has made his drive to clean up the party the hallmark of his leadership. The crackdown has felled at least 30 provincial and ministerial officials and more than 50 executives of state companies since Xi took charge — the biggest purge of its kind in decades.
Among them, those believed linked to Zhou’s case include the former chairman of CNPC, a deputy general manager there, a provincial deputy party boss, a provincial deputy governor and a deputy public security minister.
Bringing Zhou to trial is fraught with risk for the party leadership. Xi might claim a victory against corruption, but the case could expose how the party’s unchecked rule makes fertile ground for shady ties between powerful politicians and business interests.
No specific details were released on the allegations against Zhou. But reports by the financial news magazines Caixin and Caijing, and a prominent newspaper, The Beijing News, have detailed how Zhou’s son, Zhou Bin, built a business empire in oil and real estate through connections that were not explicitly stated but that clearly hinted at Zhou.
Zhou Bin also was business partners with Liu Han, a former multi-millionaire mining tycoon who was sentenced to death in May on charges of running a criminal gang.
Although Xi’s anti-corruption crackdown has been largely popular with a public eager for cleaner government, moves against high-level officials are often seen as politically motivated swipes at rivals. Political experts have said Xi’s leadership might be better served by moving away from such campaigns and improving institutional checks on power.
‘‘They should move toward building a stronger legal, political, institutional base,’’ Cheng Li, an expert on elite Chinese politics at Brookings Institution, said in a recent interview. ‘‘I think that Xi and Wang Qishan will continue this kind of anti-corruption campaign, but if it goes on and touches on too many other leaders, it could be very, very dangerous.’’
___Associated Press writers Christopher Bodeen and Ian Mader contributed to this report.