Cuban prosecutors have formally charged six people with crimes of terrorism after a US-flagged speedboat was involved in a deadly shootout with Cuba’s coast guard last week.

The US-based Cuban defendants are accused of packing a boat with weapons and heading toward Cuba in hopes of destabilising the government in Havana.

The coast guard shot and killed four other people aboard the boat, which came within one nautical mile of the Caribbean island’s shores in the 25 February shootout.

At least two of those on the speedboat were US citizens, one of whom was killed.

The defendants will be “remanded into provisional detention,” the attorney general’s office said in a statement.

There was no further update as to the condition of the wounded detainees, nor their whereabouts at a time of heightened tensions between the US and Cuba. Washington has effectively halted all oil shipments to the Communist-ruled island while demanding political and economic changes. Donald Trump’s administration has made no secret of its desire for regime change in Cuba.

Cuban officials have alleged the purported infiltrators came armed with nearly 13,000 rounds of ammunition, 13 rifles and 11 pistols, displaying the captured armaments from the studio on a special television program on Friday.

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 (66 feet).

Cuba has said at least two of those taken into custody had been previously placed on a list of accused terrorists.

Cuba’s interior ministry alleged the men came from the US with the intent to sow chaos and attack military units on the island.

Prosecutor Edward Robert Campbell told state television on Friday the accused faced a host of possible charges including crimes associated with terrorist acts.

If convicted they could face prison terms of up to 15 years for the lesser offences and 20 to 30 years – or even the death penalty – for the more serious charges, Campbell said.

US politicians have expressed skepticism over Cuba’s version of events, calling for independent investigations. The secretary of state, Marco Rubio, said it was not a US operation and that no US government personnel were involved.

Last week, Havana said Washington was willing to cooperate in the investigation.

After the Cuban revolution in 1959, such infiltration attempts by armed commandos from South Florida were not uncommon.

With Agence France-Presse and Reuters