China's former security chief Zhou Yongkang has been accused of involvement in the murder of his ex-wife, according to a report by U.S.-based news site Boxun on Friday.
The website also said that Zhou, 71, who is the highest-ranking political ally of jailed former Chongqing chief Bo Xilai, had attempted to assassinate President Xi Jinping.
Chinese political analysts have typically regarded Bo's downfall—the biggest scandal to hit the ruling Chinese Communist Party in decades—as typical of a behind-the-scenes power struggle at the heart of the party.
The reports come amid a flurry of rumors and unconfirmed reports in overseas media detailing Zhou's involvement in a widening party probe in recent days.
Taiwan media have reported that Zhou and his current wife are being held under house arrest at their home, while Boxun said that two of the family's employees had confessed to being instructed to kill Zhou's ex-wife by running her down with two cars at the turn of the century.
The two drivers, both members of the People's Armed Police, were convicted and sentenced to 15 to 20 years in prison, but released after serving just three to four years, going on to gain new jobs in the state-run petroleum industry, which was dominated by Zhou and his allies, the report said.
Hong Kong's South China Morning Post newspaper reported in late August that the leadership had agreed to open a corruption investigation into Zhou Yongkang.
But sources with ties to the leadership told Reuters at the time that Zhou was helping authorities with the investigation into the state energy companies and, contrary to media reports, and wasn't its target.
Zhou's son, Zhou Bin, is under quasi-detention on the outskirts of Beijing, helping party investigators with the inquiry, according to Pin Ho, editor of New York-based Chinese news magazine Mingjing News.
"Zhou Bin is deeply entangled ... in the anti-corruption probe into [state-owned oil giant] PetroChina ... and is now under house arrest with his wife as of Sunday evening," Ho said.
"[I have heard that] Zhou Yongkang's secretary Tan Hong, bodyguards and chauffeurs are also under investigation by the central commission for discipline inspection," he added.
"However, this report is hard to confirm," he said.
But he added: "The secretary of the commission, Wang Qishan, gave an update on the progress of the Zhou Yongkang case to the Politburo on Thursday."
Former top Communist Party aide Bao Tong, who has been under house arrest at his Beijing home since serving a seven-year jail term in the wake of the student-led pro-democracy movement of 1989, called on the government to make public details of any investigation into Zhou.
"They have released no information to date," Bao said. "Perhaps this is because they fear things will become unstable."
"But the best way to ensure stability is to tell the truth to the people."
Zhou served as public security minister from 2002, before being promoted to the all-powerful Politburo Standing Committee between 2007 and 2012, in charge of domestic security, including the widely-feared state security police.
Under Xi Jinping, Zhou's post as head of the political and legal affairs commission was downgraded after his retirement, amid widespread concern that it had become an independent and overly powerful fiefdom that contributed to the Bo Xilai scandal.
Shenzhen-based political commentator Zhu Jianguo said the sentencing of Bo to life imprisonment for corruption and abuse of power was a sign that China's leadership were increasingly using the criminal justice system as a weapon in internal power struggles.
"In the past, these would have been struggles about political ideology, or accusations of being anti-party or anti-state," Zhu said.
Beijing-based legal scholar and former top-level government adviser Yu Meisun said Zhou was guilty of great evil.
"This sort of violent and cruel suppression in the name of stability—China as a police state—is getting worse and worse," Yu said. "Online, people are talking about a blood debt, and [the system] is certainly stained with blood and tears."
"If you have a system like that, then you will get a person like that running it," he said. "Zhou Yongkang ... perpetrated heinous crimes."
Zhu likened Zhou, meanwhile, to Stalin's secret police chief and deputy premier Lavrentiy Beria.
"He's a lot like those of the ruthless era of ancient Chinese palace politics," he said. "Those who hold high office use this ruthlessness as a tool, but ultimately, when there's a backlash against it, [the system] sacrifices them."
Zhou was reported by state media has having offered condolences to the family of a respected educator who died last month.
He was last seen in public at the China University of Petroleum National Day celebrations on Oct. 1.
Reported by Wen Jian and Jiang Pei for RFA's Mandarin Service and Hai Nan for RFA's Cantonese Service. Translated and written in English by Luisetta Mudie.