The Cuban government says its forces have shot and killed four Cuban nationals on a US-registered speedboat that entered its waters and opened fire on a patrol boat.
It added that six others on the speedboat, who are also Cuban citizens, were injured and have been detained.
The Cuban commander of the border patrol boat was also wounded, according to Cuba's interior ministry.
In a statement, the ministry said the 10 passengers on the speedboat, which it claims was registered in Florida, had been living in the US and that "according to preliminary statements by those detained, intended to carry out an infiltration for terrorist purposes".
It said the passengers were armed and that most "have prior records involving criminal and violent activity".
Assault rifles, handguns, and Molotov cocktails were among the items seized, the statement added.
The ministry identified the six people detained and said two are wanted by Cuban authorities "based on their involvement in the promotion, planning, organisation, financing, support or commission of actions carried out in the national territory or in other countries, in connection with acts of terrorism".
The ministry also identified one of the dead and said efforts were under way to identify the other three.
The government said another Cuban national had been arrested, adding that he "had been sent from the United States to facilitate the landing and reception of the armed group and has confessed to his role".
US secretary of state Marco Rubio said no US government personnel were involved but insisted: "We are going to have our own information on this, we are going to figure out exactly what happened."
He said the US would try to determine if those in the incident were US citizens or permanent residents.
How the incident unfolded
The speedboat came within one nautical mile of a channel on Falcones Cay, on Cuba's north coast, when it was approached by five members of a Cuban patrol unit, the interior ministry said in an earlier statement.
The crew of the speedboat then opened fire, wounding the commander of the Cuban vessel, the statement added.
It said the injured were evacuated and given medical attention.
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Florida's attorney general James Uthmeier said he was ordering prosecutors to open a separate investigation with other state and federal law enforcement partners.
"The Cuban government cannot be trusted, and we will do everything in our power to hold these communists accountable," he wrote on X.
Florida congressman Carlos Gimenez, a Cuban-American former mayor of Miami, demanded an "urgent" investigation into what he called a "massacre".
It comes amid a time of heightened tensions between the US and Cuba following increased pressure from Donald Trump's administration.
The two countries previously collaborated on combating drug smuggling and other crimes, but have ceased to do so.
The US has also blocked virtually all oil shipments to the island, piling pressure on its communist-run government.
(c) Sky News 2026: Cuba says its forces have killed four Cuban nationals on US-registered speedboat
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