Piracy experts said Thursday that most of the hijacked ships off the coast of Somalia had ignored safety precautions, and up to 25 percent of the commercial ships that pass through the Gulf of Aden continue to do so.

An informal band of nations and organizations fighting piracy along Somalia's vast and lawless coastline vowed to try to persuade more merchant vessels to follow precautions adopted by the world's leading shipping, cargo and insurance organizations.

These self-protective measures, ranging from increased lookouts to zigzag maneuvers to the use of razor wire and fire pumps, are based on recommendations by the European Union's maritime security center for the Horn of Africa. The pirates usually seize the ships or the crews without harming them, and they often receive what they want _ tens of millions of dollars in ransom, paid in cash.

Diplomats told the anti-piracy group that both industry and the U.N. Security Council had helped the effort _ the 15-nation council by giving countries authorization to enter Somalia's territorial waters, with advance notice, and use "all necessary means" to stop piracy and armed robbery at sea.

"We are seeing the effects of the preventive measures taken by the industry," said Carl Salicath, a senior adviser at Norway's Ministry of Foreign Affairs, which chaired a daylong meeting at U.N. headquarters. It was the fifth such meeting of the so-called Contact Group on Piracy off the Coast of Somalia since its formation last year.

"The successful hijacks are almost exclusively on ships not complying with the best management practices adopted by this group. This is by far the most important measure against piracy," Salicath said. "But still, only 70 to 75 percent of the ships passing through the Gulf of Aden follow the preventive measures. Our challenge is to achieve a much higher level of compliance."

Salicath said another big factor is the military's protective naval escorts, and other counterpiracy measures, in the region. The group also has agreed to set up international funds to help pay the cost of prosecutions and beefed-up security.

Charles Petrie, a U.N. deputy special representative for Somalia, said U.N.-sponsored anti-drug efforts also are playing a role.

Somali pirates now hold nine major vessels hostage and about 200 crew members, plus about six to seven Arab sailing dhows with an undetermined number of crew members, said Captain Paul Chivers, chief of staff for the EU's naval operation off the coast of Somalia, known as Operation Atalanta.

Chivers noted most of the attacks are by pirates in 20-foot (6-meter) open boats or "skiffs" attached to a "mother ship" that venture hundreds of miles (kilometers) from shore, along a coastline roughly the size of the East Coast of the United States. He said the pirates usually hold ships for a minimum of six weeks, while negotiations are held for ransom.

"The number of attacks has gone up; the number of successful attacks has gone down," Chivers told a news conference. "It would be dangerous to assume we have overcome the threat."

The International Maritime Bureau said this month that sea attacks worldwide rose 39 percent last year to 406 cases, the highest in six years. Somali pirates accounted for 217 of the attacks and seized 47 vessels. The number of attempted hijackings was nearly double the 111 attacks Somali pirates launched in 2008.

Chivers said more merchant ships must adhere to the recommended safety precautions. "The idea is that the longer you can deter a pirate getting on board, certainly in the Gulf of Aden, the quicker we can get a war ship to them," he said.