BEIJING — China's top leaders have endorsed a corruption investigation into a former security czar who was until recently one of the country's most powerful politicians, a Hong Kong newspaper said Friday, in what would make him the most senior official targeted for graft in recent decades. Rumors about an investigation into Zhou Yongkang began swirling as early as April of last year because of his close association with disgraced politician Bo Xilai, who became embroiled in a scandal over his wife's murder of a British businessman and who stood trial last week for corruption and abuse of power. The English-language South China Morning Post, quoting sources “familiar with the leadership's thinking,” said China's current and retired top leaders reached the decision to investigate Zhou, who oversaw China's massive state security apparatus and served on the Politburo Standing Committee, the apex of political power. The decision was made in early August during a secretive meeting at a seaside resort town, the report said. The SCMP report said the investigation will focus on oilfield and property deals that have benefited Zhou and his family. The Hong Kong newspaper's report could not be independently verified. Requests for comment were faxed to the State Council Information Office, the Cabinet's press office, and the Communist Party's propaganda department while calls to the Ministry of Supervision rang unanswered. It has been several decades since a Politburo Standing Committee member has been prosecuted by China's judiciary, whether incumbent or retired. The reported investigation into Zhou, 70, may illustrate the new leadership's determination to exempt nobody in its fight against endemic corruption. But in a political system in which graft is rampant, party-steered corruption probes into senior officials have often carried political overtones. Prosecutions of high-level officials on graft charges are perceived as moves to ostracize those who have been defeated in factional struggles, without publicizing details of infighting that depict party leaders in a state of disunity. “I think that the anti-corruption effort is just a political weapon used to take down whoever they want to take down,” said Zhang Lifan, a Beijing historian and elite politics expert. “Because when there is widespread institutional corruption, anti-graft efforts are not going to clean up the system. They are a means to get rid of political opponents.” Zhang said Zhou's fate appeared to be still unclear because of media reports that the former leader sent a wreath to the memorial of a party veteran earlier this week. “That's a sign that he still has political presence,” Zhang said. Before his retirement last November during a leadership transition, Zhou was the No. 9 ranking official in the Communist Party, after rising through party ranks over 50 years. He spent the early part of his career in the state-run oil sector, eventually becoming general manager of China National Petroleum Corp., the country's biggest oil and gas company. Later, he headed the ministry of land and resources and served as party chief of Sichuan province before being put in charge of public security in the early 2000s. Zhou wielded enormous influence over the police and paramilitary forces charged with maintaining internal stability at a time of growing unrest, and he was also perceived to exert control over the oil sector through his associates. But reports in overseas Chinese media said early last year that Zhou was being scrutinized for being an outspoken ally of ousted politician Bo. Zhou was widely believed to be grooming Bo as his successor and supporting Bo's bid for a seat on the Standing Committee. The Hong Kong newspaper's report follows announcements by Chinese authorities of investigations into four high-level oil sector executives this past week as well as earlier graft probes into officials in southwestern China believed to be closely linked to Zhou. — AP