BEIJING (REUTERS) - A Chinese court on Thursday upheld the death sentence for a former mining tycoon connected to the eldest son of former domestic security chief Zhou Yongkang, the focus of a high-profile corruption investigation, state media reported.

The High People's Court in central Hubei province rejected the appeal by Liu Han, the former chairman of unlisted Hanlong Group, who received the death sentence in May, the official Xinhua news agency said.

The case against Liu is one of the most prominent featuring a private businessman since President Xi Jinping took office last year and began a campaign against pervasive graft.

Liu, who once ranked as China's 230th richest person, went on trial in March, along with others in the 36-member group, for running what state media called a "mafia-style" gang and murder.

China last week announced a probe into Zhou Yongkang, one of its most influential politicians of the last decade, in a case that has its roots in a power struggle in the ruling Communist Party.

Sources have told Reuters Liu was once a business associate of Zhou's eldest son, Zhou Bin. State media have not explicitly linked Liu's case to Zhou Yongkang, but have said his rise coincided with Zhou's time as Sichuan's party boss.

The party has already gone after several of Zhou's proteges, including Jiang Jiemin, who was the top regulator of state-owned enterprises for just five months until last September, when state media said he was under investigation for graft.

The court also upheld the death penalty for Liu's younger brother, Liu Wei, according to Xinhua. The death sentences will be handed to the Supreme People's Court for approval.