MOMBASA, Kenya Somali pirates fired grenades and automatic weapons at an American freighter loaded with food aid but the ship managed to escape the attack and was heading today to Kenya under U.S. Navy escort, officials said.

In defiance of President Barack Obama's vow to halt their banditry, pirates have seized four vessels and more than 75 hostages off the Horn of Africa since Sunday's dramatic rescue of an American freighter captain.

One pirate declared today they are grabbing more ships and hostages to prove they are not intimidated by Obama's pledge.

"Our latest hijackings are meant to show that no one can deter us from protecting our waters from the enemy because we believe in dying for our land," Omar Dahir Idle told The Associated Press by telephone from the Somali port of Harardhere.

The Liberty Sun's American crew was not injured in the latest attack but the vessel sustained some damage, owner Liberty Maritime Corp. said.

Still, the attack foiled the reunion between the American sea captain rescued by Navy snipers and the 19-man crew he had saved with his heroism.

Capt. Richard Phillips was planning to meet his crew in the Kenyan port of Mombasa and fly home with them today to Andrews Air Force Base in Maryland. But Phillips was on the USS Bainbridge, the destroyer diverted to escort the Liberty Sun after it evaded attack.

Instead, the crew was at Mombasa airport today preparing to return home alone.

"We are very happy to be going home," crewman William Rios of New York City said. "(But) we are disappointed to not be reuniting with the captain in Mombasa. He is a very brave man."

Phillips had offered himself up as a hostage to save his men.

Liberty Sun sailors used the same tactic Phillips employed to foil the pirates blockading themselves inside the engine room.

The Liberty Sun "conducted evasive maneuvers" to ward off the pirates, said U.S. Navy Lt. Nathan Christensen, spokesman for the Bahrain-based 5th Fleet.

The USS Bainbridge responded but the pirates had left by the time it arrived five hours later, Navy Capt. Jack Hanzlik said.