A Chinese mining billionaire said to have links with disgraced former security tsar Zhou Yongkang and who once launched a bid for Australia’s Sundance Resources was executed for multiple murder on Monday, a court said.

Liu Han, his younger brother Liu Wei and three accomplices were condemned to death in May for “organising and leading a mafia-style group”, murder and other crimes.

Their appeals were unsuccessful and all five were put to death on Monday, the Xianning intermediate court in the central province of Hubei said on its verified account on China’s Twitter-like Sina Weibo.

The five met with their “close relatives” before the execution, the court said in a separate posting.

“The executed criminals’ legal rights were fully protected,” it added.

Liu Han led private company Hanlong, which is based in the south-western province of Sichuan and launched a takeover bid of more than $1bn for Sundance, a listed Australian iron ore firm, in 2011.

But the deal collapsed in 2013 after the Chinese firm failed to follow through. Chinese media reports said at the time that Liu Han had been detained.

Sichuan is one of the power bases of Zhou, who once enjoyed vast power as China’s security chief but whose targeting in a corruption investigation was announced in July.

The influential business magazine Caixin has reported that Liu Han once had dealings with a businessman believed to be Zhou’s son. State media have also hinted that the gang had connections to central government officials.

Zhou was handed over to prosecutors in December.

The official announcement of the long-rumoured investigation into Zhou made him the most senior member of the Communist party to be investigated since the infamous Gang of Four – a faction that included the widow of founding leader Mao Zedong – were put on trial in 1980.