The London-based International Maritime Bureau says 2003 saw the second- highest number of pirate attacks recorded worldwide since the agency started compiling statistics in 1991.

In its annual report, the bureau says there were 445 attacks on ships and other vessels - up 20 percent from 2002. Twenty one sailors were killed. More than double the year before. More than 120 people were hurt or injured and 71 crewmembers or passengers remain missing and are presumed dead.

The Maritime Bureau also notes methods used by pirates have become more ruthless, with more guns be used and more kidnappings for ransom occurring.

The report expresses particular concern over more tankers being targeted. Terrorism experts worry these vessels, which often carry dangerous cargo, could be used as a bomb in a terrorist attack. In one recent incident, an oil tanker nearing the Singapore Straits sailed unmanned for nearly an hour after armed pirates tied up the crew and looted items from the ship.

The International Maritime Bureau says waters off Indonesia are the most hazardous, particularly in the Strait of Malacca - the world's busiest shipping lane. Bangladesh ranked second and Nigeria followed third in terms of piracy dangers.

The report called on Indonesian authorities to step up vigilance against piracy, saying efforts to stem piracy in Indonesia could "dramatically change the situation in Southeast Asia."