In Washington, US Vice-President JD Vance said the White House was “monitoring” the situation and that “hopefully it’s not as bad as we fear it could be”.
Vance added that he had been briefed by Rubio, who is attending a summit of the Caribbean Community, but “we don’t know a whole lot of details”.
The attorney-general of Florida, which lies just 160km from Cuba across the Florida Straits, ordered an investigation into the killings.
The Cuban Interior Ministry said the coastguard encountered the “illegal” US vessel, registration number FL7726SH, one nautical mile from Cayo Falcones island off Cuba’s northern coast.
As the coastguard vessel approached, “shots were fired from the illegal speedboat”, injuring the commander of the Cuban vessel, the ministry said.
“As a result of the clash, at the time of this report, on the foreign side, four aggressors were killed and six others were wounded,” the ministry said, adding that the injured were evacuated and received medical assistance.
It did not give the exact origin of the boat.
The Cuban Government frequently reports incursions by speedboats from the US into its territorial waters.
The interior ministry said it was still investigating the incident and remained committed to protecting Cuban waters.
Incursion incidents are often related to people-smuggling to the US or drug-trafficking, and have included chases, shootouts and armed attacks on border guards.
Shortages of food and medicine and daily blackouts drove an exodus from the island in recent years, with many heading to southern Florida, which has received waves of Cuban migration since the 1960s.
Between January and June 2022, the year of the largest wave of Cuban emigration in six decades, the coastguard intercepted 13 speedboats coming from the US, in what authorities described as “human trafficking operations from Cuba to that country”.
The shootings today came as Washington softened a virtual oil siege of the island imposed by US President Donald Trump in January after the US ouster of top Cuba ally, Nicolas Maduro of Venezuela.
Before Maduro’s capture by US forces on January 3, Cuba had relied on Venezuela for about half its fuel needs.
Faced with an outcry from Caribbean leaders, worried that starving Cuba of oil would cause the economy to quickly collapse, Washington said it would allow shipments of Venezuelan oil for “commercial and humanitarian use”.
The Treasury Department said the exports would need to go through private businesses and not the Cuban Government or the military apparatus which controls much of the island’s economy.
The announcement came during a summit of Caribbean nations attended by Rubio, a Cuban-American who has spent his career hoping to topple Havana’s Government.
Since becoming the top US diplomat, Rubio has toned down his calls for regime change in Havana.
The US oil blockade in place for over a month has brought an already crumbling Cuban economy to the brink.
Canada today announced C$8 million ($9.7m) in humanitarian aid for Cuba, where the blockade has worsened fuel shortages, blackouts and deepened an economic crisis.
Canada’s Foreign Ministry said the aid would be channelled through the United Nation’s World Food Program and children’s agency Unicef to ensure it “reaches the Cuban people directly”.
Mexico yesterday dispatched two military vessels carrying nearly 2200 tonnes of aid to the island - its second aid shipment in under a month.
-Agence France-Presse
