Thousands of people across China have been jailed in campaigns lawyers say are modelled on the brutal and lucrative anti-mafia drive of fallen politician Bo Xilai, who was this week sentenced to life behind bars for corruption.

As head of the southwestern megacity of Chongqing, Bo masterminded a crackdown that saw thousands of arrests, several executions, televised trials and lurid tales of a mafia "godmother" who kept a stable of 16 male partners.

But the campaign, known as "strike the black", also drew allegations of torture to extract confessions and illegal confiscation of suspects' assets, and when Bo's political career imploded in scandal last year, details of secret torture bases surfaced in Chinese media.

Private business owners were a particular target, and critics say the drive was aimed at increasing the clout of state-backed enterprises and boosting government coffers.

"Business owners were labelled as mafia members, and their property was taken," said Li Zhuang, a defence lawyer for one alleged Chongqing gang member, who was himself jailed for providing evidence that his client had been tortured.

"The money was never received by the central government, it was kept by local police," said Li, who has written that more than 100 billion yuan ($16 billion) may have been seized during the campaign.

"Bo Xilai personally approved each arrest during the crackdown... he was hoping to raise money for his political campaigns. He needed money for self-promotion."

Li's accusations are echoed by entrepreneur victims of the campaign, which saw close to 5,000 arrests after its launch in 2009.

The crackdown was overseen by Wang Lijun, the politician's flamboyant police chief and right-hand man, whose flight to a US consulate blew the Bo scandal open.

"Wang and Bo were more terrifying than the Japanese invasion," said one prominent Chongqing businessman, who was arrested twice, and asked not to be named for fear of reprisals.

"The campaign was about asserting political authority and making private business owners obey," he said.

But Bo's efforts won him plaudits from top politicians, with state media quoting Xi Jinping -- now president -- praising him for "cracking down on criminal gangs and ensuring social safety".

Accolades for Bo, who was convicted Sunday of bribery, embezzlement and abuse of power -- in a case analysts see more as a political power play than an anti-graft initiative -- encouraged officials in other areas to launch their own crackdowns, legal experts say.

"Chongqing's campaign was an encouragement. A lot of regions sent officials to Chongqing to study it," Beijing-based lawyer Zhou Ze told AFP.

In the southern province of Guizhou nearly 60 people were accused of mafia crimes, replicating tactics from Bo's political playbook, he said.

They included his client, businessman Li Qinghong, who was given a 15-year prison sentence after a confession Zhou says was extracted by torture.

'Use of torture widespread'

"In Guizhou... so many people were labelled as mafia members, so criminals and non-criminals were both pursued... use of torture was widespread," he said.

Wang Yang, a member of the ruling Communist Party's elite 25-member Politburo, launched an anti-mafia crackdown last year in the southern province of Guangdong, which he headed at the time.

Among hundreds caught was US citizen Vincent Wu, whose lawyers told media he was chained upside down and beaten before being told to confess membership of a triad crime organisation.

In Fujian in the east more than 2,700 mafia members were arrested last year, according to state media. One local suspect, Zheng Longjiang, was beaten and deprived of sleep before confessing, his lawyer said in a blog post.

In Hubei in central China, more than 2,400 people have been arrested on organised crime charges since 2012, according to state-run media.

"A lot of cities imitated Bo... the results of his campaign are huge," Li Zhuang said.

China introduced anti-mafia laws in 1997 to prevent the spread of gang organisations from Hong Kong and Macau as they returned to Beijing's control.

But lawyers say the courts have stretched the legal definitions beyond recognition.

"Anti-mafia charges are like a big bag, anything can be put in to pursue social stability," said Zhou.

"The powers of anti-mafia agencies have not been limited, and the result is that regions are free to do as they please, and arrest anyone they wish."

Nonetheless, Bo's heavy investment in policing proved popular with Chongqing residents.

"I'm not sure if Chongqing had a mafia... but the city is a lot safer because of 'strike the black'," said taxi driver Xie Zehuang.

Organised crime groups operating with the protection of local officials and police are common in China, experts say. A recent study by the Australian National University found that "strike hard' programs have failed to curb their growth.

But the campaigns -- which net both wealthy business owners and government officials -- exploit a vein of resentment against the wealthy that runs deep in Chinese society, Zhou Ze said.

"Ordinary people don't understand what a mafia organisation is, but they hate rich people and officials," he said. "If you knock down a rich person, or an official, people will clap and cheer."