A Chinese court has sentenced a businessman holding a US passport to 20 years in prison on charges of heading a mafia-style group that illegally detained rivals and operated casinos.

Guangzhou Intermediate People's Court, in Guangdong province, said in a statement late on Thursday that Hu Weixing, also known as Vincent Wu, operated casinos that netted 48 million yuan ($7.8 million).

Since 2004, Hu had gathered his family members and other ex-convicts to carry out illegal activities including coercive land requisitions, operating gambling houses and causing illegal injury, the verdict said.