Somali pirates captured an Italian-flagged tugboat with 16 crew including 10 Italians, in the latest hijacking in the Gulf of Aden.
The tugboat, with enough fuel and food on board to last a month, was believed to be heading toward the Somali coast, according to the head of the Italian company, Micoperi Srl, that owns the boat.
He denied reports the 75-metre-long tugboat was US-owned, saying his company had recently purchased it.
NATO alliance officials on a warship in the region had previously described the boat as US-owned, Italian-flagged.
In a separate incident Somali pirates were repelled by the crew on a a 26,000-tonne Panama-flagged bulk carrier, in the Gulf of Aden during a hijack attempt.
They were driven away by sailors spraying them with water-hoses.
NATO officials on board a Portuguese warship protecting the shipping lanes from piracy said an unexploded rocket-propelled grenade landed in the commanding officer's cabin during the attack and bullets were fired at the ship.
Pirates on a German ship with 24 foreign hostages said they had returned to the Somali coast after failing to locate the scene of a standoff involving a US captive on a drifting lifeboat.
The pirates had hoped to use the hijacked 20,000-tonne container vessel, Hansa Stavanger, as a shield to reach fellow pirates holding ship's captain Richard Phillips far out in the Indian Ocean. US naval ships are said to be close to the lifeboat.
The German ship was seized off south Somalia between Kenya and the Seychelles and has a crew of 24.
The guided missile destroyer USS Bainbridge is already in the area.
Officials in Washington confirmed reinforcements were nearby.
The frigate USS Halyburton is equipped with guided missiles and helicopters.
The USS Boxer, an amphibious assault ship, was also heading for the lifeboat's general area, mainly in case its medical facilities were required.
Somali elders and relatives of pirates holding Phillips are planning a mediation mission to secure his release.
Separately, French special forces stormed a yacht held by pirates elsewhere in the Indian Ocean in an assault that killed one hostage, but freed four.
The yacht Tanit was hijacked en route to Zanzibar last weekend with two couples and a three-year-old child aboard.
Florent Lemacon, father of the little boy, was the dead yachtsman.
Two pirates were killed and three captured.
