Attacks on shipping by increasingly sophisticated Somali pirates in the Gulf of Aden and the Indian Ocean reached record levels in the first nine months of the year, the International Maritime Bureau says.

Indian shipowners, who have been increasingly hit as pirates have extended their raids up to 1,500 nautical miles east of the gulf, deep into the India Ocean, say the piracy scourge is costing the global shipping industry more than $9 billion a year.

U.S. risk management company Aon reports there has been a 267 percent year-on-year increase in attacks in the Arabian Sea.

The attacks are carried out mainly by Somali pirates.

IMB Director Pottengal Mukundan says there were 352 attacks on shipping worldwide in the January-September period, up from 289 in the first nine months of 2010.

"But what's significant," he said, "is that the number of hijackings is down."

Pirates have only seized 24 ships so far in 2011, compared to 35 in the equivalent period last year. This has been attributed to more vigorous action by naval forces -- and more ships carrying armed guards, a practice once considered too provocative to be effective.

Various naval forces are deployed off Somalia and across the Indian Ocean. These include the European Union's Operation Atalanta, NATO's Operation Ocean Shield and the U.S.-led Combined Task Force-151, as well as independent flotillas from countries such as China, Iran, India and Russia.

"While such forces have been extremely active in counter-piracy efforts, the area of ocean to be patrolled, more than 1 million square kilometers, makes it an impossible task to monitor all shipping and prevent all possible attacks," the International Institute for Strategic Studies, a London think tank, observed in an analysis Tuesday.

"As a result, the shipping industry is turning to private security firms to fill the gap."

British Prime Minister David Cameron announced Oct. 30 that British-flagged ships will be allowed to carry armed guards against pirates. Up to 200 British merchant vessels regularly sail through the waters where the pirates lurk.

The British say armed guards -- previously discouraged by London -- would only be permitted to operate while passing through dangerous waters.

Cameron, asked whether he was comfortable with allowing private security operatives to "shoot to kill," told the BBC: "We have to make choices.

"The fact that a bunch of pirates in Somalia is managing to hold to ransom the rest of the world and our trading system is a complete insult and the rest of the world needs to come together with much more vigor."

Peter Hinchliffe, secretary-general of the International Chamber of Shipping, which represents more than 80 percent of the world's merchant fleet, observed: "To date, no ships with armed guards on board have been captured."

For many shipowners, this is the clinching argument, even though Hinchliffe cautioned that if the use of armed guards becomes widespread, the pirates "will respond with increase firepower to overwhelm the armed guards and, when that happens, the impact on the crew will be pretty dreadful."

The change in British thinking on this issue reflects a wider shift by governments, shipping companies and maritime organizations, including seamen's unions, toward providing armed guards on their flag vessels.

France and Spain allow armed detachments on their vessels. Italy is planning to do so as well.

When the piracy crisis in the Gulf of Aden emerged five years ago, with sea bandits from lawless, strife-torn Somalia striking largely in coastal waters in speedboats using rocket-propelled grenades, the general consensus was that armed guards would risk worsening the problem.

But now the stakes are infinitely higher. The pirates, organized mainly along clan lines, have evolved into highly sophisticated groups. They use "mother ships," usually hijacked modern fishing trawlers, to penetrate deeper into the Indian Ocean for extended voyages and capable of launching multiple attacks.

There are believed to be 7-10 gangs financed by moneymen in the Persian Gulf with agents in London's shipping insurance fraternity who identify targets with the most valuable cargoes for ransom.

The pirates' targets include oil and chemical supertankers sailing in and out of the Persian Gulf with cargoes worth hundreds of millions of dollars. This has caused great alarm that oil and gas supplies could be disrupted, driving up global prices as the world grapples with economic meltdown.