An American businessman is standing trial in China for allegedly heading a violent mob that kidnapped rivals and operated illegal casinos, charges he says he was tortured into confessing.

The trial of Vincent Wu and 31 of his associates opened Monday in the southern city of Guangzhou.

Wu's lawyer Li Zhuang says Wu's defense team told the judge that Wu is an American citizen and should be treated as such.

Chinese authorities refuse to acknowledge Wu's U.S. citizenship because he last entered mainland China on his Hong Kong residence pass.

Wu has been denied U.S. consular access since his June 2012 detention.

Wu's case underscores the risks faced by individuals working in China who have travel documents from more than one country because Beijing does not recognize dual nationalities. (AP)