Four Cubans were killed and six others were wounded when the Cuban coast guard opened fire on a U.S.-registered speedboat on Wednesday, the Cuban Interior Ministry said.

The Cubans were injured after the speedboat opened fire on the Cuban coast guard, which had been patrolling the area.

The Cuban government said in a statement that the 10 people on board the boat, including some with criminal records, were armed and had “infiltrated for terrorist purposes.”

U.S. Secretary of State Marco Rubio said his country was investigating what he called an “absolutely extraordinary” incident.

The Cuban government said that guns, rifles, explosives and other military equipment were found on the speedboat and that a coast guard officer was injured in the shooting.

US Secretary of State Marco Rubio said that the US did not trust the information provided by Cuba and announced that they would conduct their own investigation into the incident.

The incident occurred at a time when tensions between Cuba and its ally Venezuela have been high due to a fuel shortage in the country following the US blockade of fuel supplies to the country.

After the US invaded Venezuela and took over the government of President Maduro, a ally of Cuba, fuel supplies to Cuba from Venezuela have fallen sharply.