A Chinese court has convicted a mining billionaire said to have links with former security tsar Zhou Yongkang of murder and sentenced him to death.

Liu Han led private company Hanlong, which once launched a billion-dollar bid for an Australian firm.

He and his brother Liu Wei were found guilty of "organising and leading a mafia-style group", murder and other crimes, the Xianning Intermediate People's Court said.

They and three accomplices were sentenced to death.

The Liu brothers' gang, based in the southwestern province of Sichuan, killed eight people and wounded many others over nearly 20 years, the court said in a posting on China's Twitter-like Sina Weibo.

"Liu Han and Liu Wei had extremely malicious intentions, their acts were exceptionally atrocious, their social influences were extremely vile and their crimes and the consequences were extremely serious," it said.

"They should be severely punished according to the law."

Another 31 people were given penalties ranging from suspended death sentences - normally commuted to life imprisonment - to three years in jail, state media said.

Sichuan is one of the power bases of Zhou Yongkang, who once enjoyed vast power as China's security chief but is now at the centre of rumours about a corruption investigation.

He has not been seen in public for months.

State media have also hinted that the Liu brothers' gang had connections to central government officials.

The court said they were "sheltered by staff members of state organs".

Liu's Hanlong group is a diversified firm with interests ranging from tourism to minerals, and has assets of more than €4 billion.

It launched a takeover bid of more than €1.4 billion for listed Australian iron ore company Sundance Resources in 2011.

But the deal collapsed last year after the Chinese firm failed to follow through. Chinese media reports said at the time that Liu had been detained.