BEIJING - Former Chinese security chief Zhou Yongkang, the highest ranking ex-official to be investigated for corruption in decades, was sentenced Thursday to life in prison at a secret trial, state-media said.

Zhou admitted to charges of "bribery, abuse of power and leaking state secrets," at a secret trial in the northern city of Tianjin, the official Xinhua news agency said in a surprise announcement.

Zhou, 72, is a former member of the ruling Communist party's all-powerful Politburo Standing Committee, and wielded vast power as head of the police and courts until his retirement in 2012. Zhou "admitted guilt and expressed regret," Xinhua said, adding he would not appeal and that the court ruled to confiscate his personal property.

The court was cited by Xinhua as saying that Zhou and a number of associates received more than 2.1 billion yuan ($338 million) in profits from various illegal business activities. Zhou himself was convicted of taking bribes of about 130 million yuan, Xinhua said.

China's President Xi Jinping has vowed to bring down high-ranking officials in a campaign against endemic corruption, with a number of former senior officials placed under investigation since he came to power in 2012. But critics say that lack of systemic reforms mean the drive is little more than an excuse for political infighting.

After months of rumours, the party announced in July that Zhou was being investigated, before he was expelled and arrested last December.

China's courts are tightly controlled by the Communist Party and have a near-perfect conviction rate, meaning Zhou was virtually certain to be found guilty. Xinhua added that the trial was "not open," because some of the facts of Zhou's crimes involve state secrets,". The hearing's date was not announced in advance.

The length of the trial was not given by Xinhua which said it included video testimony from Zhou's wife and son. The report linked Zhou to former China National Petroleum Corporation (CNPC) head Jiang Jiemin, but did not mention disgraced former Politburo member Bo Xilai, who Chinese media had linked with Zhou.

Zhou was a central figure in what some analysts have termed an "oil faction" within the Communist Party, a network of influential politicians who have ties with China's petroleum industry - and is sometimes described as "China's Dick Cheney".

In 2002 he ascended to the upper echelons of Chinese leadership, with a slot in the ruling party's 25-member Politburo and the role of minister of public security.

Five years later he stepped up to the Politburo Standing Committee and was responsible for China's internal security, including police, courts, jails and domestic surveillance.

His tenure was marked by the brutal use of force in response to civic unrest, and stepped-up controls on dissidents and those publically challenging the Communist party.