The State Department on Friday warned Americans to keep out of Cuba, saying that some of the mystery sonic attacks targeting US diplomats took place at hotels popular with tourists.

“Over the past several months, 21 US Embassy employees have suffered a variety of injuries from attacks of an unknown nature,” Secretary of State Rex Tillerson said in a statement.

“The affected individuals have exhibited a range of physical symptoms, including ear complaints, hearing loss, dizziness, headache, fatigue, cognitive issues, and difficulty sleeping. Investigators have been unable to determine who is responsible or what is causing these attacks,” he said.

No American civilians have been affected, he added, “but the attacks are known to have occurred in US diplomatic residences and hotels frequented by US citizens.”

The department also issued a formal travel warning, and said it was pulling more than half of its diplomatic staff from the island nation and would not issue visas in Cuba until further notice.

The decision deals a blow to already dicey ties between the US and the communist country, longtime enemies who only recently began putting their bad blood behind them.

Several lawmakers have called on the administration to expel all Cuban diplomats, but Team Trump has so far declined to kick anybody out.

In May, Washington asked two to leave, but emphasized it was to protest Havana’s failure to protect diplomats on its soil, not an accusation of blame.

Although State has called them “incidents” and generally avoided deeming them attacks, officials said Friday the US now has determined there were “specific attacks” on American personnel in Cuba.

Though officials initially suspected some futuristic “sonic attack,” the picture has grown muddier.

The FBI and other agencies that searched homes and hotels where incidents occurred found no devices.

And clues about the circumstances of the incidents seem to make any explanation scientifically implausible.

Some US diplomats reported hearing various loud noises or feeling vibrations when the incidents occurred, but others heard and felt nothing yet reported symptoms later.

In some cases, the effects were narrowly confined, with victims able to walk “in” and “out” of blaring noises audible in only certain rooms or parts of rooms, the AP has reported.

Though the incidents stopped for a time, they recurred as recently as late August.

But not everyone believes the diplomats were the targets of attacks, with one expert writing that it was more likely a bungled surveillance operation.

John Sipher, a foreign policy and intelligence expert, shared that theory in an essay for Just Security, an online forum for the analysis of US national security law and policy.

“My experience in a number of similar hostile, high counterintelligence threat countries suggests that this is more likely a surveillance effort gone wrong, [rather] than the use of an offensive sonic weapon,” he wrote.

“We have very little experience anywhere in the world with directed attacks designed to physically harm our diplomats. However, the use of intrusive technical collection and surveillance, which sometimes causes harm in its own right, is consistent with past practice in Cuba and elsewhere.”

With Post Wires