The violent attack on a cruise liner off Somalia's coast shows pirates from the anarchic country on the Horn of Africa (search) are becoming bolder and more ambitious in their efforts to hijack ships for ransom and loot, a maritime official warned Sunday.

Judging by the location of Saturday's attack, the pirates were likely from the same group that hijacked a U.N.-chartered aid ship in June and held its crew and food cargo hostage for 100 days, said Andrew Mwangura, head of the Kenyan chapter of the Seafarers Assistance Program (search).

That gang is one of three well-organized pirate groups on the 1,880-mile coast of Somalia (search), which has had no effective government since opposition leaders ousted a dictatorship in 1991 and then turned on each other, leaving the nation of 7 million a patchwork of warlord fiefdoms.

Illustrating the chaos, attackers in Somalia's capital, Mogadishu (search), 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 (search).

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 (search).

U.S. and NATO warships patrol the region to protect vessels in deeper waters farther out, but they are not permitted in Somali territorial waters. Despite those patrols, the heavily armed pirates approached the cruise ship about 100 miles at sea, underlining their increasing audacity.

The International Maritime Bureau has for several months warned ships to stay at least 150 miles away from Somalia's coast, citing 25 pirate attacks in those waters since March 15 — compared with just two for all of 2004.

Somali pirates are trained fighters with maritime knowledge, identifying targets by listening to the international radio channel used by ships at sea, Mwangura said.

"Sometimes they trick the mariners by pretending that they have a problem and they should come to assist them — they send bogus distress signals," he said. "They are getting more powerful, more vicious and bolder day by day."

Maritime officials worry that the pirates could one day open fire on a chemical tanker, causing damage that would likely disrupt shipping in the region, Mwangura said.

A British maritime union on Sunday called for the world's nations to provide more protection for ships sailing by Somalia.

Andrew Linnington of the National Union of Marine Aviation and Shipping Transport, which represents merchant navy officers, said the union would meet with ship owners this week to discuss the escalating piracy in that region.

"It's got to the stage where it's anarchy on the sea waves and this latest incident shows it's time governments got their acts together," Linnington said in London.

This summer, the Semlow was the first U.N.-chartered ship to be seized while on a humanitarian mission to Somalia and the 10 crew members were held for more than three months while the pirates tried to get the United Nations to pay ransom — which it refused to do.

The hijackers agreed to let the ship go after it ran out of fuel amid negotiations by clan elders.

The gunmen who shot at the Seabourn Spirit never got close enough to board the cruise ship, but one member of the 161-person crew was injured by shrapnel, according to the Miami-based Seabourn Cruise Line, a subsidiary of Carnival Corp.

The liner escaped by shifting to high speed and changing course. Its passengers, mostly Americans with some Australians and Europeans, were gathered in a lounge for safety and none were injured, the company said.

Mark Rogers, one of the passengers aboard the Seabourn Spirit, told AP Radio he was awakened Saturday by the sound of the bullets, then he said two rockets were launched at the boat.

He described the experience as frightening, but said the crew responded very well.

"It was absolutely amazing how little panic there was," he said

The liner was bound for Mombasa, Kenya, at the end of a 16-day voyage from Alexandria, Egypt. It was expected to reach the Seychelles on Monday, then continue on its previous schedule to Singapore, company officials said.

The 440-foot-long, 10,000-ton cruise ship, which is registered in the Bahamas, sustained minor damage, the cruise company said. The liner, which had its maiden voyage in 1989, can carry 208 guests.