HAVANA, Cuba—Cuba’s coastguard shot dead four people and injured six others travelling in a US-registered speedboat in an exchange of fire off the Cuban coast on Wednesday, the interior ministry in Havana said.

The “illegal” Florida-registered boat was detected one nautical mile from Falcones Cay in Villa Clara province, the ministry said in a brief statement.

As a coastguard vessel approached to identify the boat “shots were fired from the boat,” injuring the commander of the Cuban vessel, the ministry added.

“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.

The ministry said that it remained committed to “protecting its territorial waters.”

The firefight comes amid heightened tensions between the United States and the communist island, which lies just 100 miles (160 kilometers) across the Florida Straits.

It came as Washington softened a virtual oil siege of the island imposed by 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.”