It sounds like a plot from one of John Le Carre's spy novels set in the Cold War. American and Canadian officials are investigating reports that their diplomats in Havana have been targeted by a mysterious sonic weapon.
Unidentified officials have told US media that embassy staff may have been harmed by a device fired either inside or outside their residences in Havana. A US state department spokeswoman would not give details on the nature of the injuries or how many people were affected, but confirmed that a number of US diplomats had returned home for treatment.At least two staff are said to be suffering serious health problems as a result of the alleged "sonic attack".
Canada confirmed that one of its diplomats in Cuba has been treated for hearing loss. "We are aware of unusual symptoms affecting Canadian and US diplomatic personnel and their families in Havana," said Brianna Maxwell, spokeswoman for the Canadian foreign ministry. "The government is actively working — including with US and Cuban authorities — to ascertain the cause."
US officials refused to directly blame Cuba itself for the "incidents", which appear to have begun last year, and Havana insisted it is working to protect the US mission.
Some countries have developed sonic and ultrasonic weapons that can be used for crowd control or, for example, to deter seaborne pirates without resorting to lethal force. But there are no known cases of such a device being deployed by hostile intelligence services or terrorists against a diplomatic mission.
State department spokeswoman Heather Nauert said investigations are continuing and stressed Washington was not directly blaming Cuba. But she stressed that Cuba, as host nation to the US mission, bears responsibility for its security.
Of the reported victims, she said: "What I can tell you is that these were US government personnel who were in Cuba, in Havana, on official duty on behalf of the US government. They have had a variety of physical symptoms. This is an active investigation, and it is a major concern of ours."
Ms Nauert said US personnel began experiencing ailments in late 2016, but that it was not immediately recognised that it could be anything other than an ordinary health issue.
Cuba's foreign ministry said US officials had alerted it to "some alleged incidents affecting some officials of that diplomatic mission and their families" on February 17.
Later, after the departure of some American staff, US officials asked two Cuban diplomats to leave Washington in response.
"US government officials have been physically affected by these incidents," Ms Nauert said, explaining the decision. "It is the Cuban government's obligation under the Vienna Convention to ensure the safety and protection of our diplomats there."
Cuba objected to the expulsion of its officials, but said it was treating the mystery "with the utmost seriousness" and also urged the United States to co-operate in getting to the bottom of it and to share information. Security around the US mission was also being tightened, the foreign ministry said.
Relations between the United States and Cuba broke down in 1961 at the height of the Cold War and the US embassy was closed. But ties were restored in 2015 by then US president Barack Obama and his Cuban counterpart Raúl Castro.
The mission reopened as a "special interests section" rather than a full embassy under an agreement between Cuban leader Fidel Castro and US President Jimmy Carter in he 1970s. But American diplomats were hardly made welcome. Anti-American propaganda was displayed around the compound, which Cuba saw as a base for nurturing sedition. .
Despite the rapprochement of two years ago, tensions have risen again with Donald Trump's vote-winning promises to Cuban Americans to maintain a tough line against Cuba's communist regime. In June, President Trump announced tightened rules for Americans travelling to Cuba, banned ties with a military-run tourism firm and reaffirmed the existing US trade embargo.
But however much American and Cuban diplomats may have complained to each other in the past about harassment or heavy-handed surveillance, sonic attack was never mentioned.