The People's Daily, the mouthpiece of the Communist Party, described him as "the real big tiger" but suggested that investigators have their eyes on other targets in the future.
The decision to bring him down breaks an unspoken Communist Party rule not to touch past or present members of the Politburo Standing Committee. Observers in Beijing said Zhou's demise suggests Xi Jinping, the Chinese President, has won an internal battle against Zhou's allies.
"But it has taken such a long time, so you can see how strong the forces opposing Mr Xi are," said Zhang Lifan, a political analyst in Beijing. In what is a common Communist Party tactic, the official announcement of Zhou's investigation came only after his fate had been firmly sealed.
Within minutes of the news breaking on the state media, Caijing, a Chinese magazine, said Zhou's son, Zhou Bin, was also under arrest in Hubei province for running an illegal business - a charge that carries a maximum of five years in jail.
The campaign against Zhou saw investigators chip away at his power base, hauling away at least 30 members of his family and his former political and business allies one by one. Zhan Minli, the mother-in-law of Zhou's son, told the New York Times in April that Zhou's granddaughter had been left in the care of her kindergarten in Beijing because the rest of the family is in custody. "It is too cruel for a 5-year-old child," she said.
Several commentators suggested Zhou may not be the ultimate target.
"His case is big, but Wen Jiabao's case is bigger," said one observer, who cannot be named, out of fear of reprisals. "But it is hard to tell whether they will go after Wen because his case implicates so many others," he added, referring to China's former Prime Minister. "Wen's case is hanging over the party ever since the New York Times exposed his family wealth," said another commentator, referring to an investigation that claimed Wen's family had amassed 1.5 billion ($3 billion).
