Pirates armed with guns and grenades grabbed headlines around the world last week by hijacking the 320,000-ton Saudi Arabian tanker Sirius Star 450 miles off the coast of Somalia in East Africa and holding hostage the crew of 25. The piracy was bold as the captured ship was the largest ever taken and was seized the farthest from land.

In striking contrast, five pirates armed with long knives recently boarded a tug towing a barge in the Straits of Singapore off the coast of Malaysia as it headed from Singapore to Thailand. The pirates stole personal belongings of the crew of seven, then put them ashore unharmed.

While piracy near Somalia has soared in number and audacity, that in the South China Sea in Southeast Asia has been on a steady decline, largely due to the concentrated anti-piracy operations of Indonesia, Singapore and Malaysia. Thailand has just joined the campaign while the U.S. and Japan have supported the Southeast Asians in the background.

The International Maritime Bureau in Kuala Lumpur, Malaysia, which tracks piracy worldwide, reported 49 incidents in Southeast Asia during the first nine months of 2008, down from 133 in the same period of 2004. Piracy around the Indonesian archipelago was third in the world, behind Somalia and Nigeria, on Africa's west coast, but had dropped to 23 incidents from 70 in 2004.

The IMB asserted that "the number of attacks has dropped due to the increase and constant patrols by the littoral states." Patrols at sea begin in 2004, those in the air in 2005. Moreover, the bureau said, "all except two of these cases were low level incidents aimed at theft of valuables and stores."

In addition, a lash-up between pirates and terrorists in Southeast Asia, long feared by American and Southeast Asian officials, has so far failed to materialize. Even so, intelligence agencies continue to watch this closely.

A critical part of the U.S. support has been erecting radar sites for Southeast Asian nations to track ships. If a ship deviates from its plotted course, that may be a sign it is under attack. The U.S. has also encouraged Southeast Asians to share such intelligence.

The IMB said the U.S. had given Indonesia five radar stations to provide surveillance in the Straits of Malacca and four to watch the Straits of Makassar, with three more coming. Radar stations have either been given to Malaysia, Thailand and the Philippines or are on the way.

Although piracy in that region has declined, said Capt. Jeffrey Breslau, spokesman for the U.S. Pacific Command in Hawai'i, "maritime security remains a central theme of this command's theater security cooperation program."

"The focus of discussions regarding maritime security is on partnership and cooperation among regional nations," Breslau said. "Most countries realize that building a collective capacity to defeat or deter piracy serves to promote regional stability as well as prosperity."

The Strait of Malacca and the South China Sea are important to the U.S. for military operations and to the economies of most Asian nations. They comprise the primary passageway for U.S. warships between the Pacific and Indian oceans. If that sea lane was closed, ships would need to sail routes three to five times longer.

Over the last two decades, that passage has become the world's most traveled sea line of communication. Between 50,000 to 70,000 ships a year transit this passage, more than through the Suez and Panama canals combined, particularly carrying Persian Gulf oil to China, Japan, South Korea and Taiwan.

U.S. officers said getting Southeast Asian nations to work together meant overcoming issues of sovereignty. Those nations, once ruled by the U.S., France, Britain, Portugal or the Netherlands, are jealous of the independence gained after World War II and suspicious of any encroachment on sovereignty.

The officers said they have sought first to get agencies within a nation to work together. In Indonesia, for example, 13 agencies are engaged in maritime security. Second is to get each nation to work with its next door neighbors.

Third is to foster a process in which decisions can be made rapidly. In cultures that prizes consensus, this takes patient explanation. Fourth is interdiction of a suspected pirate and communicating in a timely manner with another nation's forces.

"An advantage we have in the Pacific," said one officer, "is that we have functioning governments ashore. The first step to stopping piracy begins ashore. Without that, pirates can live and operate freely, as you see in Somalia."

Richard Halloran is a Honolulu-based journalist and former New York Times correspondent in Asia. His column appears weekly in Sunday's Focus section.