But NATO said pirates also attacked a Maltese-flagged ship before dawn with rocket-propelled grenades before the ship escaped unharmed.
The recent surge in Somali piracy has alarmed countries and businesses behind the 20,000 ships per year that cross the Gulf of Aden, the key water link between Europe and Asia. Pirates have attacked more than 80 boats this year alone, according to the Kuala Lumpur-based International Maritime Bureau.
The pirates, who work in several groups, are holding at least 17 ships and around 300 crew, and can earn $1 million or more in ransom from each ship seized.
In Monday´s attack on the Maltese-flagged MV Atlantica, two boats with about six pirates each attacked before the ship took evasive maneuvers and escaped without damages or injury, said Lt.-Cmdr. Alexandre Santos Fernandes, a spokesman for the NATO alliance. The attack took place in the Gulf of Aden, 30 miles (48 kilometers) off the coast of Yemen.
Meanwhile, other pirates released a Togo-flagged, Lebanese-owned ship after they found out it was supposed to pick up food destined for Somalia, clan elder Abdisalan Khalif Ahmed told The Associated Press from the Somali pirate haven of Harardhere.
The MV Sea Horse was hijacked April 14 with 19 crew as it headed to India to pick up more than 7,300 tons of food destined for Somalia, UN World Food Program spokesman Peter Smerdon said.
The pirates also were paid "a reward" of $100,000 Sunday by two Somali businessmen for freeing the aid ship, said Muhidin Abdulle Nur, a pirate in Harardhere who claimed to be part of the gang that captured the ship.
The WFP is feeding 3.5 million Somalis this year, about half the country´s people. That requires shipping 43,000 tons of food every month, some 90 percent of that by sea. Flying in food aid is too expensive, and roads in the lawless country are plagued by bandits.
Also Monday, a group of European dredging firms appealed to the European Union to bolster navy patrols and protect vulnerable merchant vessels in the dangerous waters off the Horn of Africa. Pirates captured the Belgian-flagged dredger Pompei in the Indian Ocean, north of the Seychelles islands, on Saturday and turned the ship north toward Somalia.
Belgian officials said Monday they have been unable to contact the ship´s 10-man crew or their captors.
Another attempted hijacking ended Sunday with warning shots from NATO helicopters and Canadian and US warships after a dramatic, hours-long pursuit of seven pirates who tried to hijack the Norwegian-flagged tanker MV Front Ardenn in the Gulf of Aden.
No shots were fired at the tanker, which escaped by taking evasive maneuvers.
NATO forces disarmed and interrogated the bandits, then freed them, citing legal issues over arresting them. Fernandes the pirates were released because Canadian law did not allow their prosecution if they committed no crimes against Canadians or on Canadian soil.
"When a ship is part of NATO, the detention of a person is a matter for the national authorities," Fernandes said from a warship in the Gulf of Aden.
The Somali government called Sunday for the death penalty for pirates, but the announcement is unlikely to have much effect. The government barely controls a few pockets of territory in Mogadishu, the capital, and is battling an Islamist insurgency.
It has made no effort so far to curb the heavily armed pirate gangs who flaunt their wealth in Somalia´s coastal cities.
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Associated Press writers Katharine Houreld and Todd Pitman in Nairobi, Kenya; Mohamed Sheikh Nor in Mogadishu, Somalia; Aoife White in Brussels; and David Stringer in London contributed to this report.
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