The United States on Tuesday expelled 15 Cuban diplomats from the country, saying Havana had failed to protect American diplomats from mysterious attacks that have caused some of them injuries over the past few months.

The diplomats have seven days to leave the US.

Last week, the US had pulled out more than half of its diplomats in Cuba.

Secretary of State Rex Tillerson said that the US Embassy in Cuba will be reduced to only emergency personnel to “minimise the number of diplomats at risk of exposure to harm”, till the country ensures their safety.

On September 29, while pulling out some US staff and their families from Cuba, Tillerson had said that 21 embassy employees in Havana had “suffered a variety of injuries from attacks of an unknown nature” over the past few months.

“The affected individuals have exhibited a range of physical symptoms, including ear complaints, hearing loss, dizziness, headache, fatigue, cognitive issues and difficulty sleeping,” he said. “Investigators have been unable to determine who is responsible or what is causing these attacks...We continue to maintain diplomatic relations with Cuba and will continue to cooperate with Cuba as we pursue the investigation into these attacks.”

The move is likely to set back the delicate reconciliation between the two countries that endured a half-century estrangement till 2015, when former President Barack Obama and Cuban President Raul Castro restored diplomatic ties. The Donald Trump administration has, so far, not pointedly blamed Cuba for perpetrating the attacks.

The mysterious attacks

The symptoms in the attacks vary from person to person. In addition to hearing loss and concussions, some experienced nausea, headaches and ear-ringing, and some now suffer from problems with concentration and word recall.

Initially, officials suspected sonic attacks, but the Federal Bureau of Investigation and other agencies that searched homes and hotels in Cuba where the incidents occurred found no devices.

A Canadian diplomat was also affected, and this has deepened the mystery as relations between Canada and Cuba have been warm.