Russia is believed to be behind the strange “sonic attacks” that have left US diplomats with concussion-like injuries in Cuba and China, according to a report Tuesday.

Communications intercepts, known as “signals intelligence,” that point to Russia as the culprit have been collected as part of an ongoing investigation by the FBI, CIA and other agencies in the US, multiple sources told NBC News.

The evidence, though, isn’t conclusive enough to formally blame the Motherland.

Twenty-six US workers have been hurt in the attacks that occurred in their homes or hotel rooms beginning in 2016. Most reported hearing high-pitched sounds, leading investigators to suspect a sonic weapon.

The FBI later said sound waves alone couldn’t have caused the symptoms, which included brain injuries, hearing loss, cognitive problems, difficulty with balance and problems with vision and hearing.

A US employee experienced similar symptoms following an attack earlier this summer in Guangzhou, China.

Now scientists are claiming microwaves could be to blame, according to CNN.

The unexplained incidents have worsened relations between the Cuba and the US, which pulled out most of its diplomats from Havana and tossed 17 Cuban counterparts from Washington.

Cuba has denied any involvement and officials there don’t believe a sonic device is to blame.

The incidents are also being probed by the State Department’s internal Accountability Review Board.

“The State Department has come to the determination that they were attacks,” the head of the board, retired Ambassador Peter Bodde, testified before Congress last week.

A source told NBC News that the US has “no reason to believe this was anything but an intentional act.”

The Kremlin didn’t immediately respond to messages seeking comment.

Last week, a top security official in the UK pointed the finger at Vladimir Putin for the deadly nerve-agent attacks that nearly killed a former Russian spy and his daughter in England.