MUSCAT, Oman - Ordered to get inside and stay down, Oregon tourist Clyde Thornburg heard the pirates' rifle shots hit the side of the luxury cruise ship - "Pop! Pop! Pop!" - then felt the ship speed up to escape.

At this port north of the pirate-infested Gulf of Aden, passengers yesterday said that they had been warned of the danger even before they embarked, and that the crew used a device that blasted painful high-decibel sound waves to keep the marauders at bay.

The attack on the nearly 600-foot-long cruise ship in the dangerous waters between Yemen and Somalia was the latest evidence that pirates have grown more brazen, viewing almost any vessel as a potential target - even a large luxury liner with hundreds of tourists on board.

But the assault on the M/S Nautica lasted only five minutes Sunday, and the ship with about 650 passengers and 400 crew members sped away quickly and was not seized.

"We didn't think they would be cheeky enough to attack a cruise ship," said Wendy Armitage, of Wellington, New Zealand, shortly after disembarking for a daylong port stop in the Omani capital of Muscat.

During the assault, pirates on one of two skiffs fired eight rifle shots at the ship, according to its American operator, Oceania Cruises, Inc. The captain ordered the passengers inside and accelerated the cruise liner quickly, leaving the pirates far behind in their 20- to 30-foot wooden speedboats, powered with twin outboard motors.

Lynne Pincini, of Australia, said that she was heading to a friend's cabin when the order came to keep their heads down and stay inside.

"We heard the announcement, and of course we went straight out on the balcony to have a look," she said. "It was like a very large speedboat. It was running alongside the boat."

The passengers were on a monthlong cruise from Rome to Singapore, a route that took them through the Gulf of Aden between Somalia and Yemen, where pirates have hijacked dozens of vessels this year.

At the beginning of the journey, the Nautica's captain had briefed the passengers on what the vessel could do to ward off pirates.

Passengers were told that the Nautica could outrun pirates and was equipped with high-pressure water hoses and a device that blasts painful sound waves at any bandits. Such devices can emit sounds up to 150 decibels - well above the normal pain threshold of 120 decibels - focused on targets several hundred yards away. *