"Many of the vessels attacked call regularly at Nigerian ports or operate exclusively within Nigerian waters supporting the local oil industry," the IMB said in a report. "Owners may feel that it is best to resort to local measures to cope with this crime for fear of reprisals if they report the attacks."

Peru has seen increased activity by pirates, while Southeast Asian waters, including the Malacca Straits, and the Bangladeshi port of Chittagong are considered anti-piracy successes, with reported attacks sharply down from past years because of patrols and other efforts. Still, attacks on fishing and other local vessels in developing countries are routinely difficult to document.

Some robbers sneak aboard a berthed or anchored ship or yacht at night and vanish after stealing whatever they can: paint cans, mooring lines and electronic equipment. Such petty theft falls under a broad definition of piracy if the criminals are armed.

John Burnett, author of "Dangerous Waters: Modern Piracy and Terror on the High Seas," said it costs $20,000 to $80,000 a day to run a cargo vessel, and the economic fallout of reporting a crime at anchor or on the high seas can entail a costly layover in a port far from home.

"They have to stop the ship and take days for an investigation, which would probably lead nowhere," Burnett said. "The captain is frequently pressured not to make a big deal out of it."

Yusuf Capoglu of Lori Denizcilik, an Istanbul-based firm that ships iron, wheat, coal and other commodities worldwide, said he knew of three or four Turkish vessels that repelled Somali pirate attacks with water jets.

... contd.