Since November 5, when pirates tried unsuccessfully to attack a 440-foot cruise liner operated by Seabourn Cruise Lines, at least five other attacks have taken place, most of them northeast of Somalia, said Andrew Mwangura, program coordinator at the Kenyan Seafarer's Association.

Overall, he said, seven ships and crews have been taken into captivity in that section of the Indian Ocean.

Fishermen in the area spotted a "pirate mother ship" drifting off the Somali coast in July, on November 5 and earlier this week, Mwangura said. Only one mother ship has been spotted, but there may be more in existence. Officials think the smaller boats used in attacks are launched from the mother ship, he said.

A crew of more than 10 people, including a captain and engineer, are believed to be on the ship. The crew is believed to be well-organized, Mwangura said....

Earlier this week, the director of the International Maritime Bureau, appealed to vessels off the Somali coasts to come to the aid of ships under attack in a statement citing an "alarming rise" in the number of piracy attacks in the area.

"At the very least," said Capt. Pottengal Mukundan, IMB director, "they can prevent the hijackers from taking these ships into Somali waters. Once the vessels have entered these waters, the chances of any law enforcement is negligible."

Twenty-five pirate attacks have been reported in the past six months, the statement said. "In one incident, a ship was lured into danger by pirates firing bogus distress flares."...

The northern and southern coastline of Somalia -- Africa's longest -- links trade routes for key commodities like oil, grains and iron ore from the Gulf and Red Sea region down to the Mozambique Channel. Thousands of merchant ships snake down the Somali coast to the Cape of Good Hope every year.

Some of the world's leading shipping bodies called on the U.N. to urgently address the issue.

On Wednesday, the U.N. Security Council criticized Somalia's squabbling government and urged rival factions to work to confront the chaos and piracy plaguing the lawless nation.

Illustrating the chaos, attackers in Somalia's capital, Mogadishu, threw grenades and exploded a land mine Sunday near a convoy carrying the prime minister of a transitional government that has been trying to exert control since late last year.

The attack, which killed at least five bodyguards, was the second in six months involving explosions near Prime Minister Ali Mohamed Gedi, whose internally divided government spends much of its time in Kenya.

Even before the attack on the liner Seabourn Spirit, Gedi had urged neighboring countries to send warships to patrol Somalia's stretch of coast, which is Africa's longest and lies along key shipping lanes linking the Mediterranean with the Persian Gulf and Indian Ocean.