MOGADISHU, Somalia - A warship is shadowing a yacht with four Americans on board that was hijacked by Somali pirates, a pirate said Sunday, as the vessel was reported to be moving closer to the Somali coast.

The yacht Quest was hijacked on Friday off the coast of Oman, but is now in the waters between Yemen and northern Somalia, two pirates and a Somali government official told The Associated Press.

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One pirate who gave his name only as Hassan said a warship with a helicopter on its deck is near the Quest.

The pirate's claim could not be independently verified, and US officials on Sunday did not release any information about the yacht. A US Embassy spokesman on Saturday said officials were assessing options and "possible responses."

Hassan told the AP he is speaking directly with the pirates aboard the hijacked yacht. A second pirate who gave his name as Bile Hussein and a Somali official in Puntland who asked not to be named both said the Quest is in between Yemen and Somalia and heading closer to Puntland, a haven for pirates on Somalia's northern tip.

In New York, the first secretary of Somalia's UN Mission, Omar Jamal, said he had received reports from Somalia that the boat was expected to make landfall late Sunday.

Pirates have increased attacks on ships off the coast of East Africa, but Americans have rarely been targeted. The last attack against a US crew -- in 2009 -- ended with Navy sharpshooters killing two pirates and rescuing the ship's captain.

If the Quest reaches Somalia's shores the four American hostages would likely be taken inland, where a fast resolution is much less likely. A British sailing couple who were released in November spent 388 days in pirate captivity.

The organizers of an international yacht race called the Blue Water Rally said the Quest had been taking part in the race but left it Feb 15 to chart an independent course from India to Oman.

The Quest is owned by Scott and Jean Adam, a couple from California. The Blue Water organizers also identified the other two Americans onboard as Phyllis Mackay and Bob Riggle. The NBC TV station in Seattle, Washington spelled the name as Phyllis Macay and said she and Riggle are from Seattle.

"We feel desperately sorry for our four friends onboard and our thoughts are with them and their friends and family. All the yachts still on the rally are fine and well," the Blue Water website said.