Pirates fired a rocket-propelled grenade and machine guns Saturday in an attack on a luxury cruise liner off the East African coast, the vessel's owners said.

Two armed boats approached the Seabourn Spirit about 100 miles off the coast of Somalia and fired as the boats' occupants attempted to get onboard, said Bruce Good, a spokesman for Miami-based Seabourn Cruise Line, a subsidiary of Carnival Corp.

The ship outran them and changed course.

"Our suspicion at this time is that the motive was theft," Good said.

The attackers never got close enough to board the Spirit, but one member of the 161-person crew was injured by shrapnel, said Deborah Natansohn, president of the cruise line.

The Press Association, the British news agency, said passengers awoke to the sound of gunfire as two 25-foot inflatable boats approached the liner.

Edith Laird of Seattle, who was traveling on the ship with her daughter and a friend, told British Broadcasting Corp. TV in an e-mail that "at least three rocket-propelled grenades . . . hit the ship."

The vessel's 151 passengers, mostly Americans with some Australians and Europeans, were gathered in a lounge for their safety, Good said. None was injured.

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

Piracy along the Somalian coast is common -- several ships a month are attacked or hijacked, with valuables stolen and crews held for ransom.