"Some U.S. government personnel who were working at our embassy in Havana, Cuba on official duty ... reported some incidents which have caused a variety of physical symptoms", spokeswoman Nauert told reporters Wednesday.
The Cuban Foreign Ministry statement also called the USA decision to expel two Cuban diplomats based in Washington "unjustified and baseless". "She would not say what the symptoms were except that they were not life-threatening", the AP added.
United States diplomats in Cuba said they suffered occasional harassment for years after the restoration of limited ties with the communist government in the 1970s, harassment reciprocated by USA agents against Cuban diplomats in Washington.
A small number of Americans began reporting symptoms at the end of 2016, and a few were either removed for medical treatment in the USA or asked to leave, State Department officials were quoted as saying by the Washington Post on Wednesday.
After months of investigation, U.S. officials concluded that the diplomats had been attacked with an advanced sonic weapon that operated outside the range of audible sound and had been deployed either inside or outside their residences.
It's in response to a series of incidents that left American diplomats in Cuba with physical symptoms.
The Associated Press, one of the few Western news outlets with offices in the Cuban capital, reported from Havana that the injuries may have been caused by sonic equipment that Cuban intelligence officers installed in the U.S. Embassy or residences of its staff.
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The US embassy in Havana re-opened in August 2015 as part of improved diplomatic relations between the two states under Barack Obama.
After the incidents the USA retaliated by sending two Cuban diplomats, based in Washington, back to the island country.
Nauert confirmed that two Cuban diplomats were asked to leave on May 23rd and they've since departed.
Cuba said it had started a comprehensive investigation into the alleged incidents after it had been informed of them by the embassy in February.
Investigators are exploring the possibility that another country, such as Russian Federation, carried out the attack without the Cuban government's knowledge. "And we take this extremely seriously". She said the department is looking into the matter.
In June, President Trump announced announced that, "effectively immediately I'm cancelling the last administration's completely one-sided deal with Cuba".
Relations with the country have become a significant issue in U.S. politics, he explained, thanks in part to the population of Cuban exiles in Florida, a battleground state in USA elections.
The Cuban Foreign Relations Ministry (MINREX) responded to the incident in a statement published in Granma, the official newspaper of the Communist Party of Cuba (PCC). Personal harm to USA officials shows the extent the Castro regime will go and clearly violates worldwide norms.