A karaoke singer who killed six of his sex partners by hanging was executed last month, it was revealed this week. The Xiaoxiang Morning Post reported Tuesday that Zhou Youping was executed in Changsha, Hunan province on August 29 after the Supreme People's Court approved a death sentence handed down to him by the Changsha Intermediate People's Court in March 2011. He was 42. Zhou, who worked as a singer in a karaoke bar in the Hunan provincial capital, started seeking men online for sadomasochistic play in September 2009. Zhou would encourage his victims to engage in erotic asphyxiation, whereby one cuts off the supply of oxygen to the brain to increase sexual pleasure. After the men hanged themselves, Zhou didn't release them, leaving them to suffocate to death, the court said. Zhou said that he knew the dangers of the game, and never took part in it himself, but liked watching other people play. In a pre-trail interview with a local newspaper, Zhou denied killing the men. "I didn't want them dead, it was only a game," he said. Police found the bodies of six men in different hotels between October 11 and November 26, 2009. Zhou was arrested on November 28 after which he confessed to the murders, according to police. Though the Hunan Higher People's Court overturned his conviction for four of the murders, but upheld the death sentence against him for the remaining two. China's top court approved that sentence on August 29 and Zhou was executed later that day.