A U.S. surveillance plane was monitoring the ship as it continued to its destination on the Kenyan coast, while a pirate said that the captain of a ship hijacked Monday with 28 North Korean crew members on board had died of wounds.
Pirates hijacked the Maersk Alabama last April and took ship captain Richard Phillips hostage, holding him at gunpoint in a lifeboat for five days. Navy SEAL sharpshooters freed Phillips while killing three pirates in a daring nighttime attack.
Four suspected pirates in a skiff attacked the ship again on Wednesday around 6:30 a.m. local time, firing on the ship with automatic weapons from about 300 yards (meters) away, a statement from the U.S. Fifth Fleet in Bahrain said.
An on-board security team repelled the attack by using evasive maneuvers, small-arms fire and a Long Range Acoustic Device, which can beam earsplitting alarm tones, the fleet said.
Vice Adm. Bill Gortney of the U.S. Naval Forces Central Command, said the Maersk Alabama had followed the maritime industry's "best practices" in having a security team on board.
"This is a great example of how merchant mariners can take proactive action to prevent being attacked and why we recommend that ships follow industry best practices if they're in high-risk areas," Gortney said in a statement.
However, Roger Middleton, a piracy expert at the London-based think tank Chatham House, said the international maritime community was still "solidly against" armed guards aboard vessels at sea, but that American ships have taken a different line than the rest of the international community.
"Shipping companies are still pretty much overwhelmingly opposed to the idea of armed guards," Middleton said. "Lots of private security companies employee people who don't have maritime experience. Also, there's the idea that it's the responsibility of states and navies to provide security. I would think it's a step backward if we start privatizing security of the shipping trade."
A Massachusetts Maritime Academy professor, who is also the father of a sailor who was on the Maersk Alabama during the first pirate attack in April, said about 20 percent of the ships off East Africa are armed.
The owners of the Maersk Alabama have spent a considerable amount of money since the April hijacking to make the vessel pirate-proof, Murphy said, including structural features and safety equipment. The most dramatic change is what he called a security force of "highly trained ex-military personnel."
"Somali pirates understand one thing and only one thing, and that's force," said Capt. Joseph Murphy, who teaches maritime security at the school. "They analyze risk very carefully, and when the risk is too high they are going to step back. They are not going to jeopardize themselves."
The wife of the Maersk Alabama's captain, Paul Rochford, told WBZ-AM radio in Boston that she was "really happy" there were weapons on board for this attack.
"It probably surprised the pirates. They were probably shocked," Kimberly Rochford. "I'm really happy at least it didn't turn out like the last time."
A self-proclaimed pirate told The Associated Press from the Somali pirate town of Haradhere that colleagues out at sea had called around 9 a.m. - 2½ hours after the attack.
"They told us that they got in trouble with an American ship, then we lost them. We have been trying to locate them since," said a self-described pirate who gave his name as Abdi Nor.
A U.S. Navy P-3 surveillance aircraft "is monitoring Maersk Alabama and has good voice communication with the vessel," said Lt. Nathan Christensen, the Bahrain-based spokesman for the 5th Fleet.
"Everything is safe and secure and Maersk Alabama is proceeding to their intended destination," Christensen said. The ship was heading for the Kenyan port town of Mombasa.
Maritime experts said it was unlucky but not unprecedented that the Maersk Alabama had been targeted in a second attack.
"It's not the first vessel to have been attacked twice, and it's a chance that every single ship takes as it passes through the area," Cmdr. John Harbour, a spokesman for the EU Naval Force. "At least this time they had a vessel protection detachment on board who were able to repel the attack."
Phillips' ordeal last spring galvanized the attention of the U.S. public to the dangers of operating merchant ships in the Horn of Africa, one of the busiest and most precarious sea lanes in the world.
Underscoring the danger, a self-proclaimed pirate said Wednesday that the captain of a ship hijacked Monday had died of wounds suffered during the ship's hijacking. The pirate, Sa'id, who gave only one name for fear of reprisals, said the captain died Tuesday night from internal bleeding.
The EU Naval Force has said the Virgin Islands-owned chemical tanker the Theresa was taken Monday with 28 North Korean crew. Pirates have greatly increased their attacks in recent weeks after seasonal rains subsided. On Tuesday, a self-proclaimed pirate said that Somali hijackers had been paid $3.3 million for the release of 36 crew members from a Spanish vessel held for more than six weeks - a clear demonstration of how lucrative the trade can be for impoverished Somalis.
Phillips told the AP last month from his farmhouse in Vermont that he was contemplating retiring from sea life after his ordeal. He's been given a book deal and a movie could be in the works.
Phillips was hailed as a hero for helping his crew thwart April's hijacking before he was taken hostage, but he says he never volunteered, as crew members and his family reported at the time. He says he was already a hostage when he struck a deal with the pirates - trading him for their leader, who was taken by the Maersk Alabama's crew.
Associated Press writers Mohamed Olad Hassan in Mogadishu, Somalia, Barbara Surk in Dubai and Mark Pratt in Boston contributed to this report.