Cuba's government said late Wednesday that the 10 passengers on a boat that opened fire on its soldiers were armed Cubans living in the US who were trying to infiltrate the island and unleash terrorism.

The announcement came hours after Cuba said its soldiers killed four people and wounded six others aboard a Florida-registered speed boat that had entered Cuban waters and opened fire on the soldiers first, injuring one Cuban officer.

Cuba's government said the majority of the 10 people on the boat "have a known history of criminal and violent activity."

It identified two of them as Amijail Sanchez Gonzalez and Leordan Enrique Cruz Gomez, who are wanted by Cuban authorities "based on their involvement in the promotion, planning, organization, financing, support or commission of actions carried out in the national territory or in other countries, in connection with acts of terrorism."

The government said it also had arrested Duniel Hernandez Santos, adding that he was "sent from the United States to guarantee the reception of the armed infiltration, who at this time has confessed to his actions."

The Associated Press was not immediately able to independently verify that information.

Cuba's government said it obtained the details about the passengers aboard the boat from the suspects detained following the shootout.

It identified seven of the 10 passengers, including Conrado Galindo Sariol, Jose Manuel Rodriguez Castello, Cristian Ernesto Acosta Guevara and Roberto Azcorra Consuegra. Cuba's government said that one of the four killed was Michel Ortega Casanova. Three others have not yet been identified.

"The investigation process continues until the facts are fully clarified," the ministry said in a statement.

US Secretary of State Marco Rubio had told reporters earlier that he was made aware of the incident and that the US is now gathering its own information to determine if the victims were American citizens or permanent residents.

"We have various different elements of the US government that are trying to identify elements of the story that may not be provided to us now," Rubio said while at the airport in Basseterre, St Kitts, where he was attending a regional summit with Caribbean leaders.

US President Donald Trump's top diplomat refused to speculate on what happened, saying that it could be a "wide range of things," and that the US will not solely rely on what the Cuban authorities have provided thus far.

"Suffice it to say, it is highly unusual to see shootouts in open sea like that. It's not something that happens every day. It's something, frankly, that hasn't happened with Cuba in a very long time," Rubio said.

He said both the US Department of Homeland Security and the US Coast Guard are investigating the incident and stressed that he wants to verify the facts.

"The majority of the facts being publicly reported are those by the information provided by the Cubans. We will verify that independently as we gather more information, and we'll be prepared to respond accordingly," Rubio said. "We're going to have our own information on this. We're going to figure out exactly what happened."

He said it was not a US government operation and that he wasn't "going to speculate about whose boat it was, what they were doing, why they were there, what actually happened."

Rubio added: "We are going to know, and when we know, then we'll tell you, and we'll do what needs to be done about it, depending on what it is."

Rubio said he found out about the shooting before the Cuban government posted on social media, noting that the US has "constant contact" with the country "at the Coast Guard level."

Earlier, Cuba's Interior Ministry issued a statement that provided few details about the shooting, but noted that the boat was roughly 1 mile (1.6 kilometres) northeast of Cayo Falcones, off Cuba's north coast.

The government provided the boat's registration number, but The Associated Press was unable to readily verify details of the boat because boat registrations are not public in the state of Florida.

It wasn't immediately known what the boat and its occupants were doing in Cuban waters. In the statement, the ministry said Cuba's government was "safeguarding its sovereignty and ensuring stability in the region."

US Vice President JD Vance said late Wednesday afternoon that Rubio had briefed him on the incident. He added that the White House was monitoring the situation.

"Hopefully it's not as bad as we fear it could be," Vance said.

The shooting threatens to increase tensions between the US and Cuba. Following the ouster of Venezuelan President Nicolas Maduro, President Donald Trump and top administration officials have taken an increasingly aggressive stance toward Cuba, which had been largely kept economically afloat by Venezuela's oil.

The energy crisis Cuba has been grappling with in recent years entered new extremes last month when Trump signed an executive order that would impose a tariff on any country that sells or provides oil to Cuba. The move put pressure on Mexico, which Cuba became largely dependent on for petroleum after Trump halted oil shipments from Venezuela.

America's top diplomat says a dramatic shift must be made by Cuba's government because that's the only way to improve the quality of life of its citizens.

Rubio says the government needs to make "dramatic reforms that open the space for both economic and eventually political freedom for the people of Cuba."

Meanwhile, James Uthmeier, Florida's attorney general, said he has ordered prosecutors to work with federal, state and law enforcement partners to start an investigation.

"The Cuban government cannot be trusted, and we will do everything in our power to hold these communists accountable," he wrote on X.

It's not unusual for skirmishes to erupt between Cuba's Coast Guard and US-flagged speedboats in Cuban waters, but there have been no recent reports of passengers opening fire or being killed.

In past years, some of those US-flagged boats were laden with unidentified items headed toward the island or they were going to pick up Cubans and smuggle them into the US.