The mysterious death of a major Russian oil executive has left as many questions as it has brought answers. 

Lukoil, Russia’s largest private oil company, said its chairman Ravil Maganov “passed away following a severe illness,” Thursday at age 67.

But citing two sources familiar with his death, Reuters reported that he died after falling from the window of the Central Clinical Hospital in Moscow. Several Russian media outlets, citing sources from law enforcement agencies, have also suggested that he was trying to smoke when he plunged to his death.

NBC News has not verified how he died and Maganov’s family has remained silent on the matter. The hospital and police declined to comment, and Russia’s Investigative Committee did not return requests for comment.

However, several Western commentators have noted that Lukoil, the country’s second largest oil producer, came out against Russian President Vladimir Putin’s war a few days after his forces invaded Ukraine, calling for it to end. 

 And while no political link to Maganov’s death has been established, several people who have chosen to cross the Kremlin have died suddenly and in unexplained circumstances. 

Risky business:

“There has been a remarkable number of suspicious deaths in recent months of senior executives connected with the oil and gas industry,” John Lough, an associate fellow at London’s Chatham House think tank, told NBC News via email Thursday. 

“It is reminiscent of the banditry of the 1990s in Russia during the first phase of privatization after the collapse of the USSR,” added Lough, who specializes in Russian affairs.

Maganov’s death follows the passing of seven other senior Russian energy executives since the start of the year. Among them was his former top Lukoil executive Alexander Subbotin, whose body was discovered in the basement of a country house in the Moscow region in May, police in the city said.

Other senior executives from natural gas giants Gazprom and Novatek, as well as Vladislav Avayev, the former vice president of Russia’ third largest bank Gazprombank, have also died.    

“This suggests there is some serious infighting taking place in the sector connected to access to financial flows,” Lough said. 

Olga Oliker, the program director for Europe and Central Asia at the International Crisis Group in Brussels, said that “trend” was the wrong word to describe the deaths She said there were enough incidents to argue that Russian state policy either allows for political assassinations or that it lacks control over its security services and does not have the capacity to prevent them.

“There are enough incidents that those who run afoul of Russian leadership, or appear to, may well worry about potential threats to their lives,” she said.