A former top boss of one of Russia's biggest state-owned oil companies died after receiving a dubious treatment from a "shaman" over the weekend, Russian media say. Lukoil board member Alexander Subbotin, who no longer held a management role at the firm, was found dead in Mytishchi, a town just outside Moscow, in a house owned by a local healer or medicine man known as Magua, according to state news agency TASS.

Online news outlet Mash said Magua and his wife were offering high-paying clients various unorthodox treatments, including a procedure involving poisonous toads.

"They would make an incision on the skin, dripped toad poison there, and after the patient vomited, he allegedly would feel better," Mash claimed, alleging that Subbotin had been a frequent customer who came seeking treatment for hangovers.

"Suddenly, he felt unwell, and his heart ached. The shaman decided not to call an ambulance, gave him some usual heart drops and put the billionaire to sleep in the basement, where he later died," Mash reported, adding: "Whether Alexander got sick from poisonous toads or something else is not clear, but the investigation will soon figure it out."

TASS, one of Russia's biggest news outlets, said the local ambulance service got an emergency call reporting a man who had lost consciousness after suffering an apparent heart attack on May 8. The doctor who arrived on the scene declared Subbotin dead, said TASS, citing a law enforcement source. 

According to the news agency, the Ministry of Internal Affairs launched a criminal case that will include testing Subbotin's blood for drugs of any kind.

TASS' source appeared to confirm some details of Mash's reporting, saying Subbotin had visited Magua, whose real name is Alexey Pindurin, after "a state of severe alcohol and drug intoxication [sustained] the day before."

"The body of the billionaire was in the basement of Pindyurin's house, in a room used for Jamaican voodoo rituals," TASS said.