Fifteen Cuban diplomats have been expelled from the US after Havana failed to protect US diplomats from mysterious acoustic attacks.
The Cuban personnel have been given seven days to leave.
The State Department’s move follows last week’s US withdrawal of more than half of its own diplomats from the Cuban capital.
Nearly two dozen US personnel have suffered ill health after unexplained attacks in Havana.
Secretary of State Rex Tillerson said in a statement on October 3: “The decision was made due to Cuba’s failure to take appropriate steps to protect our diplomats in accordance with its obligations under the Vienna Convention. This order will ensure equity in our respective diplomatic operations.”
At least 21 people working at the US’s embassy in Havana have reported health problems, ranging from mild brain trauma and deafness to dizziness and nausea.
Earlier reports suggested sonic attacks were to blame, but nothing has been proven.
Havana denies targeting embassy staff, and the US has not blamed the Cuban government for the suspected attacks.
Rex Tillerson added in his latest statement: “We continue to maintain diplomatic relations with Cuba, and will continue to co-operate with Cuba as we pursue the investigation into these attacks.”