The government in Havana has said 10 Cuban nationals coming from the United States entered Cuban waters and opened fire on a border guard vessel, leading Cuban forces to return fire killing four and wounding six others, who were taken into custody.
In an attempt to dispel doubts about its account to date, senior Cuban Interior Ministry officers displayed the captured armaments from the studio on a special television program, including bins full of at least some of the 12,846 recovered rounds.
They also showed pictures of the vessels, each peppered with bullet holes from the firefight they said took place at a range of 20 metres.
The confrontation took place at a fraught moment in US-Cuban relations, with US President Donald Trump pressuring the island by imposing a virtual oil blockade after capturing and ousting Venezuelan President Nicolas Maduro, a crucial Cuban ally, on January 3.
Cuba has identified the assailants as Cuban exiles, some of whom had been previously placed on a list of accused terrorists, who came from the United States with the intent to sow chaos and attack military units on the Communist-ruled island.
"The intent of this group is to infiltrate, to promote public disorder. To incite the people to unite. To carry out something violent. Attack military units in order to incite social unrest and to unite the people in order to steal the revolution. That has been duly proven," said Colonel Victor Alvarez of the Interior Ministry.
US politicians have expressed skepticism over Cuba's version of events. Secretary of State Marco Rubio on Wednesday said his government would independently investigate, adding it was not a US operation and no US government personnel were involved.
Cuban officers said the infiltrators set out from Marathon in the Florida Keys on two vessels but ditched one at some point due to technical difficulties.
They united on one speedboat, which a US official said was reported stolen in Florida. Cuba said it recovered a drone, radios, knives, a portable power plant, bolt cutters and other materiel.
They also found emblems of the November 30th Movement and People's Self-Defense, anti-communist groups that oppose the Cuban government.
Cuba says a patrol of five border guard members on a nine-metre boat spotted the incoming vessel shortly after 7am, with some members of the incoming crew in the water, about one nautical mile off a cay on the Caribbean island's northern coast, about 160 km from Marathon.
The infiltrators opened fire at a distance of 185 metres, striking the captain of the Cuban vessel in the abdomen, Cuba said.
Bleeding heavily, the wounded captain remained at the helm and steered toward the enemy vessel, leading to a firefight at a distance of about 20 metres, the officers said.
Cuba called its response "proportional."
The captured Cuban nationals were receiving medical care and face charges including armed aggression, illegal entry into national territory, crimes associated with terrorist acts, and arms trafficking, prosecutor Edward Robert Campbell told the program.
He said they face prison terms of up to 10 to 15 years for the lesser offences and 20 to 30 years - or even the death penalty - for the more serious charges.
