A notorious Hong Kong gang leader, known as Big Spender, has been executed in China amid controversy over the fairness of his trial.

Cheung Tze-keung had been convicted of a series of high-profile crimes committed in Hong Kong, including armed robbery, smuggling guns and explosives, and kidnapping business tycoons.

Human rights activists argued that mainland China has no jurisdiction over crimes committed in Hong Kong, where there is no death penalty.

Amnesty International called the trial unfair rejecting the court's argument that the crimes had been plotted on the mainland.

Within an hour of the verdict in the southern city of Guangzhou Cheung and four other accused were taken away and shot.