MOMBASA, Kenya - Somalian pirates captured four more ships and took more than 60 crew hostage in a brazen hijacking spree, while the American captain who escaped their grip planned to reunite with his crew and fly home Wednesday to the United States.

Capt. Richard Phillips of the Maersk Alabama has been hailed as a hero for offering himself up as a hostage to save his crew. In a dramatic rescue, U.S. navy SEALs shot three pirates dead Sunday night to free Phillips after a five-day standoff.

Phillips and his 19-man crew will reunite in the Kenyan port of Mombasa on Wednesday and fly from there to Andrews Air Force Base in Maryland on a chartered flight, according to the shipping company Maersk. They will be reunited with loved ones at Andrews in a private reception area.

Pirates have vowed to retaliate for five colleagues slain by U.S. and French forces in hostage rescues in the last week, and the top U.S. military officer said Tuesday he takes those comments seriously.

But Admiral Michael Mullen, chairman of the Joint Chiefs of Staff, told ABC's "Good Morning America" that "we're very well prepared to deal with anything like that."

Despite Mullen's confident statement and President Barack Obama's warning of further U.S. action, pirates captured two more nautical trophies Tuesday to match the two ships they seized a day or two earlier.

The latest seizures were the Lebanese-owned cargo ship MV Sea Horse, the Greek-managed bulk carrier MV Irene E.M. and two Egyptian fishing boats. Maritime officials said the Irene carried 21 to 23 Filipino crew and the International Maritime Bureau reported 36 fishermen, all believed to be Egyptian, on the two boats.

It was not known exactly how many crew the Sea Horse had, but a ship that size would probably need at least a dozen sailors.

NATO spokeswoman Shona Lowe said pirates in three or four speedboats captured the Sea Horse off Somalia's eastern coast Tuesday - an attack that came only hours after the Irene was seized in a rare overnight raid in the nearby Gulf of Aden.

The two Egyptian fishing boats were hijacked in the gulf off Somalia's northern coast but it was not clear if those attacks came Monday or Sunday.

The Gulf of Aden, which links the Suez Canal and the Red Sea to the Indian Ocean, is one of the world's busiest and most vital shipping lanes, crossed by over 20,000 ships each year. It has been at the centre of the world's fight against piracy.

A flotilla of warships from nearly a dozen countries has patrolled the Gulf of Aden and nearby Indian Ocean waters for months. They have halted many attacks on ships this year, but say the area is so vast they can't stop all hijackings.

Pirates have attacked 78 ships this year, hijacking 19 of them, and 17 ships with over 300 crew still remain in pirates' hands, according to Noel Choong, who heads the International Maritime Bureau's piracy reporting centre in Kuala Lumpur.

Each boat carries the potential of a million-dollar ransom.

A senior U.S. defence official in Washington said Phillips was being debriefed Tuesday on the USS Bainbridge. Among other questions, FBI officials and maritime experts are keen to know exactly what each hostage-taker did, to gather evidence for possible criminal investigations or to better prepare for future hostage situations.

It was not clear exactly who was interviewing Phillips. The official spoke on condition of anonymity because he was not authorized to speak on the record.

A fourth pirate who had been holding Phillips was in U.S. custody after surrendering.

The Irene, flagged in the Caribbean country of St. Vincent and the Grenadines, was sailing from the Middle East to South Asia, said Choong.

Lt. Nathan Christensen, spokesman for the Bahrain-based U.S. 5th Fleet, said the Irene carried 23 Filipino crew, while Choong reported it had 21 and Greek marine officials said it carried 22. There was no immediate way to reconcile the figures.

A maritime security contractor, speaking on condition of anonymity because it is a sensitive security issue, said the Irene put out a distress signal "to say they had a suspicious vessel approaching. That rapidly turned into an attack and then a hijacking."

"They tried to call in support on the emergency channels, but they never got any response," the contractor said.

The four pirates who attacked the Alabama were between 17 and 19 years old, Defence Secretary Robert Gates said.

"Untrained teenagers with heavy weapons," Gates told students and faculty at the Marine Corps War College. "Everybody in the room knows the consequences of that."

U.S. officials were now considering whether to bring the fourth pirate, who surrendered shortly before the sniper shootings, to the United States or turn him over to Kenya. Both piracy and hostage-taking carry life prison sentences under U.S. law.