MOMBASA, Kenya -- Pirates seized two freighters Tuesday in the Gulf of Aden off Somalia, NATO and EU officials said.

Crew members aboard a 35,000-ton Greek ship were thought to be unharmed after being kidnapped, said the EU Maritime Security Center.

Just hours later, a second ship was hijacked, said NATO officials, who offered no further details.

Meanwhile, the rescued captain of a U.S. ship was en route Tuesday to Mombasa, Kenya, to join his crew, CNN reported.

Richard Phillips was freed Sunday when U.S. Navy snipers killed three pirates aboard a lifeboat where they held Phillips hostage after their attempt to hijack his ship failed. A fourth pirate was being held by U.S. authorities for prosecution, CNN said.

Phillips, sailing Tuesday aboard the USS Bainbridge, was to join his crew at a beach resort in Kenya before returning home to the United States.

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