WASHINGTON – The U.S. Navy is adopting more aggressive tactics to counter piracy off the coast of Somalia, helping last week to make the area free of captured vessels for the first time since February, according to a senior U.S. Navy commander in the region.

The pirates, Somali clansmen and trained fighters armed with AK-47 assault rifles, operate in small skiffs as far as 200 miles offshore, according to the U.S. military. They have hijacked and held as many as six merchant ships for ransoms of millions of dollars since February, the military said.

In the past, the pirates counted on being able to flee into territorial waters, but in recent months U.S. naval ships have gained permission to pursue them and cut off their access to fresh supplies.

“We positioned the ships and helicopters … to have complete visibility between the beach and the pirated vessel,” said Vice Adm. Kevin Cosgriff, commander of U.S. Naval Forces Central Command and the U.S. 5th Fleet. Two U.S. ships at a time, each with about 300 sailors, were involved in the operations, part of a broader maritime security mission around the Horn of Africa, he said.

“We told them, “You will not be able to resupply, and if you want to send a boat out to remove yourselves, you have to ask for approval,'” Cosgriff said Friday in a telephone interview from his headquarters in Bahrain.

In addition, the Navy has destroyed the pirate ships “as a repressive measure,” Cosgriff said. “They were disabled” with gunfire, “cut adrift, and sunk as hazards to navigation.”

In the latest incident, the pirates hijacked the Japanese-owned ship Golden Nori in October and released it Wednesday, the last of several captured vessels. The U.S. ships involved in the pursuit included the guided missile destroyer USS Porter, named after Commodore David Porter, known for his counter-piracy exploits in the West Indies in the 1820s.

Cosgriff said that at least 200 pirates operate from three camps along the Somali coast and that until now they had been “modestly successful.”

Typically, the pirates approach the merchant ships, which are usually unarmed, and threaten the crew, demanding ransom and pilfering the ship before they leave. In one incident, pirates shot a crew member and put his body in a freezer. In another, they engaged in a shootout with the crew of a North Korean cargo vessel as it left Mogadishu, the Somali capital. A U.S. ship treated the wounded North Korean crew.

AP-NY-12-15-07 1854EST