US media reports say the plane crash that is believed to have killed Wagner Group leader Yevgeny Prigozhin may have been caused by an intentional explosion.

The private jet carrying 10 people crashed on Wednesday in northwestern Russia while flying from Moscow to St. Petersburg.

Russian President Vladimir Putin sent his condolences to Prigozhin's family on Thursday.

The Wall Street Journal reported on Thursday that "the preliminary US government assessments, which officials stressed are incomplete, suggest that a bomb exploded on the aircraft or that some other form of sabotage caused the crash."

It also quoted a British official as saying that "while Western governments are still gathering information and insight into the crash, the most likely suspect of foul play would be Russia's Federal Security Service, or FSB, its domestic intelligence agency."

The New York Times reported on Thursday that US and other Western officials suspect an explosion brought down the plane, citing preliminary intelligence. The report said, "The explosion could have been caused by a bomb or other device planted on the aircraft, though other theories, like adulterated fuel, were also being explored."

US Defense Department spokesperson Pat Ryder told reporters that they assess media reports which said a surface-to-air missile brought down the plane were inaccurate.