HAVANA -- Three men charged with terrorism for hijacking a passenger ferry April 2 were executed Friday after summary trials, the government reported.

The men were prosecuted Tuesday in summary trials for "very grave acts of terrorism" and given several days to appeal their sentences, according to a statement read on state television.

However, the sentences were upheld both by Cuba's Supreme Tribunal and the ruling Council of State, and were carried out at dawn Friday, the statement said.

Capital punishment in Cuba is always carried out by firing squad. It has been used sparingly in recent years.

Another four men received life sentences, according to the statement.

No one was hurt when the group, reportedly armed with at least one pistol and several knives, seized the ferry and its 50 passengers in Havana Bay early April 2 and ordered the captain to sail to the United States.

Later that day, the 45-foot ferry Baragua ran out of fuel in the high seas of the Florida Straits, and officers on two Cuban Coast Guard patrol boats that chased them there tried to persuade the hijackers to return to the island.

The hijackers allegedly threatened to throw passengers from the boxy, flat-bottomed boat overboard but soon agreed to let the ferry be towed 30 miles back to Cuba's Mariel port for refueling.

After the boat was docked in Mariel, west of Havana, Cuban authorities eventually gained control of the ferry April 3 and arrested the suspects after a quick-thinking French woman hostage jumped into the water to confuse her captors.

The standoff ended with all the hostages, then the suspects, jumping into the water.

The seizing of the vessel came a day after a Cuban passenger plane was hijacked to Key West by a man who allegedly threatened to blow up the aircraft with two grenades, which later turned out to be fake. Ten of the Cubans aboard that flight opted to remain in the United States and 19 others asked to go home.

Another Cuban plane was hijacked to Key West less than two weeks before.

James Cason, the top U.S. diplomat in Cuba, warned after the recent incidents that hijackers would be prosecuted and would lose the right to seek American residency.

The hijackings coincided with a crackdown on dissidents in Cuba and rising tensions with the United States.