HONG KONG — A Chinese billionaire who was building a mining empire in Australia was executed Monday after a court last year sentenced him to die for running a “mafia-style” gang that engaged in murder and extortion.

Liu Han, 49, his brother Liu Wei, and three associates were executed on Monday, the state-run Xinhua news agency reported, citing the Xianning Intermediate People’s Court in the central Chinese province of Hubei. The men had been sentenced last May for running a criminal syndicate that killed at least eight people, ran extortion schemes, trafficked weapons and operated gambling dens.

Their crimes were “deeply evil and particularly cruel,” Xinhua cited the court as saying.

China leads the world in executions, but Liu Han’s case was particularly noteworthy because of his great wealth — with one official report pinning his family’s assets at more than $6 billion — his international business network that invested in Australian mines, as well as his reported connections to a disgraced former Chinese police czar who is awaiting trial.

Liu Han’s arrest in March 2013 came as he was in talks to buy the Australian mining company Sundance Resources. The deal collapsed the following month. In 2009, his flagship company, Sichuan Hanlong Group, bought a controlling stake in another Australian mining company, Moly Mines.