THE military has been called in to probe a series of bizarre "sonic attacks" on US diplomats working in Cuba and China which have left dozens sick.

Symptoms include hearing loss, tinnitus, vertigo, headaches and fatigue, which experts say is a pattern consistent with "traumatic brain injury."

Now the state department has reportedly called for a joint operation - involving the US Navy - to try and get to the bottom of the hi-tech "attacks".

Cuba has long denied any involvement in the baffling incidents which have pushed relations between the two countries to breaking point.

And an investigation by the FBI and the CIA has unearthed data that US officials say seems to point the finger of suspicion at Russia.

NBC News said the National Institutes of Health, the Centres for Disease Control and Prevention, and the Office of Naval Research, have been asked to solve the mystery.

They were called in after a two-year effort by the FBI and the US intelligence community failed to resolve what was behind the unusual incidents.

Up to 370 diplomats and their families serving in China have been tested amid concerns they could also have been affected by the attacks.

US officials said in July they were still investigating health problems at the US embassy in Cuba, and do not know who or what was behind the mysterious illnesses, which began in 2016 and have affected at least 26 Americans.

The State Department even brought a group of diplomats home from Guangzhou, China, over concerns they were suffering from a mysterious malady resembling brain injury.

Cuban officials, who are conducting their own investigation, say as of yet they have no knowledge of what was behind it.

The US believes sophisticated electromagnetic weapons may have been used on government workers, possibly in conjunction with other technologies.

The military has been working on measures that can counteract the effects of the weapon or weapons used to harm the diplomats, including by testing various devices on animals, NBC said.

Part of the work is being done at the directed energy research programme at Kirtland Air Force Base in New Mexico, where the military has giant lasers and laboratories to test high-power electromagnetic weapons, including microwaves, NBC said.

Canada has also reported 13 cases of unexplained health problems at its Cuban embassy since early 2017.