Central China Television showed a short clip of the trial on its evening newscast, in which a white-haired Zhou is seen standing and listening to the court's guilty verdict. A judge asked: "Have you heard this clearly?" Without any visible emotion, Zhou replied: "I've heard clearly."

He said he accepted the verdict and would not appeal. He also said his crimes had harmed the party and admitted to his guilt.

Zhou, 72, a former member of the Politburo Standing Committee - the highest decision-making body in the country - was formally charged in April. The trial took place on May 22. It was not open to the public because his case involved the disclosure of state secrets, Xinhua said.

On the charge of taking bribes, Zhou was sentenced to life imprisonment, had his political rights withdrawn and assets confiscated.

For abuse of power, he was jailed for seven years, and for leaking state secrets he was given four years behind bars.

The court ruled that Zhou and his family took 129.77 million yuan (HK$164 million) in bribes from his close allies.

Jiang Jiemin , the former head of the state-owned Assets Supervision and Administration Commission and former chairman of the state-run China National Petroleum Corporation (CNPC), where Zhou was a top official for 10 years, gave him 731,000 yuan, the court found.

The court said Zhou had abused his power by asking Jiang and former Sichuan deputy party chief Li Chuncheng to direct more than 2.13 billion yuan of illegal gains to his son and other businessmen, causing a loss of 1.48 billion yuan to the economy.

Zhou also gave six classified documents, five of which were top secret, to Cao Yongzheng, whom mainland media have described as a "qigong master". Most of the bribes were taken by his relatives and he had asked them to hand back the money, the court said, adding all the money had been confiscated.

Watch: Reaction to Zhou Yongkang's sentence

A commentary by said the verdict showed no one could stand above the law, and opposition to corruption had become a national consensus.

Political analysts said although Zhou was sentenced to life in jail, and the party had broken a previous unspoken rule that former members of the Politburo's elite Standing Committee would not be prosecuted, he was still let off relatively lightly, given what the court said he did.

Political commentator Li Weidong said Zhou's escape of the death sentence, unlike some lower officials who were convicted of taking much less in bribes, showed he was still treated leniently.

They said his trial arrived suddenly without publicity, compared with the open trial of his ally, former Chongqing party chief Bo Xilai in 2013, because the party did not want to further tarnish its image.

Chen Daoyin, a political scientist at Shanghai University of Political Science and Law, said the anti-corruption drive and trial of Bo had built up a "circus effect", which the party was now keen to cool.

Political commentator Ching Cheong said the verdict avoided mentioning the political reason for Zhou's prosecution, which was that he posed a threat to President Xi Jinping. 

The Supreme People's Court in March accused Zhou and Bo of "engaging in political activities [not approved by the party]".

Ching said the party wanted to play down Zhou's sentencing because it wanted to uphold its legitimacy among ordinary Chinese.

"It wants to safeguard the security of the regime," he said.

A lawyer with knowledge of the cases of Zhou and his family, who declined to be named, said the sentencing should have been open to the public.

Gu Yongzhong, one of Zhou's lawyers, said his client's right to defend himself was adequately protected.

CRIME AND PUNISHMENT

CHARGE:

Taking bribes

SENTENCE:

Life imprisonment, political rights withdrawn for life, personal assets confiscated

CHARGE:

Abuse of power

SENTENCE:

Seven years' imprisonment

CHARGE:

Leaking state secrets

SENTENCE:

Four years' imprisonment