By going after retired senior officials, President Xi Jinping has broken the Communist Party's unwritten tradition of not prosecuting a top leader once he has stepped down from power. This would send a strong message throughout the party ranks, analysts said.
Beijing on Tuesday announced an official graft investigation into ex-security tsar Zhou Yongkang , who retired from the Communist Party's highest ruling body, the Politburo Standing Committee, in 2012.
This came just a month after the leadership expelled former vice-chairman of the powerful Central Military Commission Xu Caihou from the Communist Party for similar allegations. Xu also retired in 2012.
Analysts in China and overseas believe these cases will have a far-reaching impact. Since the end of the Cultural Revolution, no retired Politburo-ranking official had been investigated for corruption - until the cases of Xu and Zhou.
"It sends a chilling message to those who still remain in power not to commit any wrongdoing or challenge the leadership, or they won't be safe even after retirement," said Beijing-based political commentator Zhang Lifan, who was formerly a historian with the Chinese Academy of Social Sciences.
"The investigations against Zhou and Xu simply mean that the top leadership is able to take down anyone if it wants," he said.
Both Xi's predecessors Jiang Zemin and Hu Jintao had launched anticorruption campaigns in the early days of their presidency.
But in both cases, they went after incumbent officials who were seen as their political rivals. This gave rise to the public impression that these high-level anti-corruption campaigns were thinly veiled power struggles.
Former Politburo member Chen Liangyu was dismissed under Hu's leadership in 2006 for misusing public funds. In Jiang's era, Chen Xitong , a Politburo member and former Beijing mayor, was taken down in 1995 on charges of corruption.
Watch: File video of Zhou Yongkang
Analysts said Xi's decision to break the tradition was because the nation's corruption problem was getting too serious, with corrupted officials forming powerful cliques with close ties to each other.
Deng Yuwen , a former editor at the Study Times, said both Zhou and Xu had already built around them a massive network of corruption which involved many incumbent officials.
"The authorities built the case against Zhou and Xu by taking down officials one by one. By targeting Zhou and Xu, serving officials are being reminded that their safety is not guaranteed even if they can survive this round and make it to retirement."
Mainland readers finally understand what's going on with Zhou Yongkang
Mainlanders finally understood the situation surrounding the man they now obliquely refer to as "you understand" when they woke up yesterday to headlines announcing that former security tsar Zhou Yongkang had been placed under official investigation.
The announcement ended months of intense speculation about Zhou, whom internet users began referring to as "you understand, don't you?" on social media after a government spokesman used the phrase in March to explain why he could not say more about the matter.
Yesterday all major state-run newspapers carried simple, near-identical front-page headlines announcing the probe into the retired Politburo Standing Committee member.
Even the typically bolder Guangzhou-based newspapers, such as Guangdong party organ Nanfang Daily and its sister paper, the Southern Metropolis Daily, played it safe, reprinting a brief Xinhua report with a People's Daily editorial.
The English-language China Daily splashed the news on its front page with the headline "Top tiger caged by graft probe". And while other papers shied away from using images of Zhou, the daily ran a large photo of him alongside smaller images of his former associates who were recently arrested.
A Yunnan newspaper, played on the tiger theme, with Kunming-based tabloid Dushi Shibao running a headline on the probe alongside a large photo of a tiger on a leash being walked on the street.
While most newspapers carried a People's Daily editorial, some published their own commentaries.
Internet users were more critical of the latest development in President Xi Jinping's far-reaching corruption crackdown.
Beijing-based Hu Jia , one of the mainland's more outspoken dissidents, said the investigation into Zhou was merely a power struggle.
Peking University law professor He Weifang said that using the anti-graft campaign to weed out one's political enemies "was not helping China's efforts to move in the right direction".
Watch: China's Xi cementing power with probe into Zhou: HK analyst