A former top Chinese economic planning official was convicted of bribery Wednesday and sentenced to life in prison after a former lover went public with a litany of accusations against him.

The guilty verdict against Liu Tienan, once deputy director of the National Development and Reform Commission, China's top economic planning agency, is the latest step of the Communist Party's much-publicised anti-corruption campaign.

"Liu Tienan is sentenced to life in prison for bribery," the Langfang Intermediate People's Court said in a document handed to AFP.

He was convicted of taking 35.58 million yuan ($5.8 million) in bribes, the document added.

It added that the case was "based on clear facts and concrete and sufficient evidence".

"The court holds that the defendant Liu Tienan as a government employee took advantage of his post to seek gains for others, illegally took cash or gifts from others by himself or via his son Liu Decheng. His activities amounted to committing the crime of bribery."

Beijing authorities picked the court in Langfang, a desolate and bleak industrial city in Hebei province, an hour's drive south of the capital, to hear the case.

State broadcaster China Central Television showed Liu facing the judge impassively in court as the verdict was read out. He wore a black jacket and trousers, and was flanked by two policemen.

Foreign media were not allowed in and there was a large police presence outside, where the road was blocked off and a parade of police vehicles drove up and down the street, while a group of protesters complained about local government wrongdoing.

Liu took bribes from various business people included cash and gifts for his son, among them a villa in Beijing and a Porsche, in exchange for project approvals and other favours, the court said during his trial in September.

He had accepted his guilt, it said then on a verified microblog account, quoting him tearfully expressing "deep repentance and remorse".

"Every round of interrogation, every sentence and even every contact with the investigators has felt like whips slashing my soul," he said.

"Faced with the facts, I have been asking myself every time I read the indictment, is this me? How did I end up being corrupted like this?"

- Mistress makes accusations -

Liu fell after his mistress gave incriminating information to a prominent journalist who then posted online her accusations of shady business deals, fake academic credentials and death threats.

Communist Party authorities have waged a much-publicised anti-graft campaign since Xi Jinping ascended to the organisation's leadership two years ago.

But critics say no systemic reforms have been introduced to increase transparency to help battle endemic corruption.

Liu had ties to powerful former security czar Zhou Yongkang and former China National Petroleum Corporation (CNPC) head Jiang Jiemin, both now under investigation for corruption.

Zhou -- who was expelled from the Communist Party and arrested last week -- also previously led CNPC and rose through the oil sector to the elite Politburo Standing Committee.

He is the most senior Communist Party official to be investigated since the infamous Gang of Four -- a faction that included the widow of founding leader Mao Zedong -- were put on trial in 1980.

Zhou's detention had been expected for months and was seen by observers as underscoring Xi's determination to consolidate his firm grip on power.

Willy Lam, a politics specialist at the Chinese University of Hong Kong, said of the proceedings against Liu: "There's a political motivation behind this case.

"If he had belonged to the right faction within the party, he would have been protected even with his dirty laundry being aired on the Internet."

He added that the anti-graft campaign was likely to focus on more officials from the powerful energy industry and bloated state-owned companies.

"The rigour with which Liu's case is being pursued shows Xi will try to tackle other sectors of the energy empire, like the nuclear companies," Lam said.