At least one American citizen was shot dead and another injured by Cuban officials intercepting a speedboat off its coast on Wednesday, a US official said.

Border guards killed four people and injured the remaining six aboard the Florida-registered speedboat. Cuba accused the 10 people on the boat of planning "an infiltration with terrorist aims" and said they opened fire first.

A third person was on a US K-1 visa for fiancées of American citizens, the US official said. The boat's owner alleged the vessel had been stolen by an employee.

US Secretary of State Marco Rubio said Washington was investigating the "highly unusual" incident. Cuban authorities had said all 10 were Cuban nationals residing in the US.

They also identified an 11th person they said had been arrested and confessed to being part of the alleged plot. The interior ministry said the speedboat entered its territorial waters and was intercepted one nautical mile off Cayo Falcones on the northern coast.

The commander of the Cuban boat was injured in the firefight. Cuban authorities added that most passengers had "prior records involving criminal and violent activity". Handguns, assault rifles, and improvised explosive devices were recovered from the speedboat.

The deadly shooting comes amid increased tension between the two countries. Cuban President Miguel Díaz-Canel vowed to defend the country against aggression. Deputy Foreign Minister Carlos Fernández de Cossío said the US had shown a willingness to cooperate on clarifying the events.

Source: www.bbc.com