A former top manager of LUKoil, Aleksandr Subbotin, has reportedly died under strange circumstances, the latest in a series of mysterious deaths of Russian businessmen since Moscow launched its unprovoked invasion of Ukraine on February 24.

Citing sources close to the Moscow regional police on May 9, media reported that forensic tests were held to find possible drugs in Subbotin’s body, which was found in a basement in a house in the town of Mytishchi near the Russian capital on May 8.

According to the sources, the owner of the house where the billionaire’s body was found, Aleksei Pindyurin, also known as Shaman Magua, testified to police that Subbotin came to his house under the influence of alcohol and drugs seeking a ritual he often asked Pindyurin to perform to relieve hangover symptoms.

Less than three weeks ago, on April 21, Vagit Alekperov, the founder and co-owner of LUKoil — Russia’s largest private oil company — resigned after he and other Russian tycoons were hit by sanctions by Australia and the United Kingdom over Moscow’s invasion of Ukraine.

The same day, media reports in Spain reported that a former top manager at Russian gas giant Novatek, Sergei Protosenya, his wife, and daughter had been found dead in a rented villa in the town of Lloret de Mar near Barcelona two days earlier.

The 55-year-old millionaire was found hanged, while his wife and daughter had been stabbed to death in the villa, police were quoted as saying.

On April 18, Vladislav Avayev, a former vice president of one of Russia’s leading financial institutions, Gazprombank, was found dead in his Moscow apartment together with the bodies of his wife and daughter.

Police said at the time that the apartment was locked from the inside and a pistol was found in Avayev’s hands, leading them to conclude that Avayev shot his wife and his teenage daughter before killing himself.

On March 24, another Russian billionaire, Vasily Melnikov, who owned the medical-supply company MedStom, his wife, and two sons were found stabbed to death in their apartment in the city of Nizhny Novgorod.

On February 28, Russian tycoon Mikhail Watford was found hanged in the garage of his home in Surrey in the United Kingdom. U.K. officials said at the time there were no signs of a foul play.

On February 25, the day after Russia launched its invasion of Ukraine, a top manager of Russia’s Gazprom energy giant, Aleksandr Tyulyakov, was found hanged in the garage of his house near St. Peterburg. Police said at the time that they found a suicide note next to the body.

Another top Gazprom executive, Leonid Shulman, was found dead in a cottage near St. Peterburg in January, weeks before Russia began its invasion. A suicide note was also found next to his body.