China media: Zhou Yongkang
Chinese papers give front-page coverage to the widely-expected announcement that former security chief Zhou Yongkang is being investigated for "serious disciplinary violation".
Mr Zhou headed China's Ministry of Public Security and was a member of the top decision-making body, the Politburo Standing Committee.
"The announcement of the investigation of former senior official Zhou Yongkang has revealed the courage and resolution of the Communist Party of China (CPC) to purify itself and run itself with strict discipline," says a Xinhua commentary.
The state-run agency says the case is a declaration that "there should be no CPC member whose behaviour can stay outside the jurisdiction of the law and discipline".
The People's Daily has published a series of articles commenting on the probe, praising the government's anti-graft effort under President Xi Jinping.
A front-page commentary in the paper, which has been reprinted by several media outlets, hails the central government's decision to "take on Mr Zhou".
"Everyone is equal in the face of the party's discipline and nobody is exceptional. The probe against Zhou Yongkang has once again proven this," it warns.
Another article on the paper's website says that the probe has "crushed the rumours" that the Politburo Standing Committee members are "immune from punishment".
The website also compares the differences in the wording used in this case with that of Bo Xilai, the disgraced former Chongqing party chief.
It says the term "comrade" was used to address Mr Bo in previous official statements, but this has not been used for Mr Zhou.
Ren Jianming, a professor of clean governance research, says the removal of the term while referring to Mr Zhou shows that "the investigation process has been completed".
"He will be sacked from the party as his violation is a serious one," he tells the daily.'Subtle timing'
Elsewhere, the China Daily notes that "many doubted Xi and his colleagues' readiness to take on such a politically risky step" because Mr Zhou had been "at the very core of the national leadership".
"That Xi and his colleagues have finally chosen not to exempt Zhou from disciplinary scrutiny speaks volumes about the present leaders' loyalty to their pledge of leaving no safe haven for abusers of power," the daily says.
The Beijing News and the Beijing Youth Daily welcome the news and point out that the probe shows the "resolution of the leadership to capture both the tigers and the flies" and "will not disappoint the expectation of the people".
Meanwhile, the Global Times observes that the CPC announced that it would hold the Fourth Plenary Session of the 18th Central Committee in October. This news came an hour after the announcement of the probe against Mr Zhou.
Noting the "subtle timing and sequence of the announcements", the paper adds that the plenary session, which has been viewed as a chance to reaffirm the policy direction of Mr Xi's administration, will discuss key issues concerning the rule of law.
Several media outlets in Hong Kong are also keeping a close watch on the development and call for more systematic reform to fight corruption on the mainland.
Analysts tell the South China Morning Post the take-down of Mr Zhou "has given the president clout not seen since Deng Xiaoping and energised his anti-graft fight".
Analysts say the high-profile case is "enough" for Mr Xi "to reinforce his message that party stars can no longer use their power bases and state-owned firms to accumulate massive wealth".
Praising the effort of the Xi administration, the Sing Tao Daily, however, calls for "system reform, as heavy-handed measures are not sufficient" to fight the problems.
Echoing similar sentiments, the Hong Kong Economic Times comments that the probe is "an important step in the long journey in the anti-graft effort".
"China will embark on the path of clean politics and social stability only when the mechanism to fight corruption is improved and perfected," it says.