LONDON (Dow Jones)-- Marine transport costs could rocket as piracy escalates in the Gulf of Aden, either because of hefty ransom payments or because shippers divert vessels onto longer routes, industry participants said Tuesday.

The capture by pirates of a Saudi Arabian oil tanker laden with 2 million barrels of oil, worth $100 million, has sent shockwaves through the shipping industry.

Based on previous ransom payments, for the vessel's owners "to get back the ship, it will cost $5 million to $10 million," said Nick Day, chief executive of Washington-based security and intelligence consultancy Diligence Inc.

Day, a former member of the U.K. Royal Navy's Special Boat Service, said ransoms totaling $80 million had already been paid to Somali pirates this year for 35 ships - a $2 million average.

As a result of the rising risk of piracy, and its associated cost, some shippers are now avoiding the area altogether.

"We will no longer expose our crew to the risk of being hijacked and held for ransom by pirates in the Gulf of Aden," said Terje Storeng, chief executive of Odfjell SE (ODF.OS), one of the world's biggest shipping companies.

Storeng said that unless the company were committed by existing contracts to sail through the Gulf of Aden area, it would now re-route ships around the Cape of Good Hope.

Odfjell's "decision is seen as a big signal in the shipping industry, [which] could spike insurance fees and spark other shippers to follow suit," said Philippe de Pontet, an analyst at risk consultancy Eurasia Group.

The Saudi vessel Sirius Star was attacked off the Kenyan coast, hundreds of miles south of the Gulf of Aden, and the incident is by far the most ambitious of a series of attacks on vessels in recent months. It has prompted shippers to publicize plans to safeguard crews, ships and cargo on voyages through areas targeted by pirates.

But not everyone considers avoiding the Gulf of Aden area viable, not least because of the additional expense. Re-routing presents a financial risk for shippers as it entails extra sailing days and later cargo deliveries, which incur significant extra costs in an already tough economic climate.

"The other option - around the Cape of Good Hope - is going to cost a hell of a lot," said Captain Mirchandani, company security officer at shipping company Navig8. "Sailing time, plus the amount of fuel you're going to burn."

"At the moment the balance is still in favor of transiting the Suez Canal but doing it prudently and recognizing all precautions that can be taken," said Lars Lundegaard, senior vice-president at Danish shipping company Norden Ltd.

"That's the important takeaway - when transiting the Gulf of Aden use maximum safe speed, use guidance from coalition warships, keep a diligent lookout and at all times be prepared with counter measures such as water hoses, signaling, maneuvering - that's the best guarantee," Lundegaard said.

He estimates that around 80% of incidents don't escalate into hijackings because pirates are deterred by counter-measures.

Diligence's Day said ships will increasingly "use a number of non-lethal means to stop people boarding ships," such as electric side-rails, high-power hoses or deafening sonic alarms.

NATO currently has four ships - from the U.K., Greece, Italy and Turkey - on patrol in the waters off Somalia, with two protecting U.N. food aid convoys to the strife-torn country. Its 'Operation Atlanta' ends in mid-December, when a bigger European Union mission is due to be put in place.

Jorgen Harling, group vice-president at Maersk Line, agrees with Lundegaard, saying all vessels are "speeding up when passing the 480 nautical miles between Yemen and Somalia and along the entire coast" until they get around the tip of Yemen, "so chances of being taken are less."

But Maersk's Harling notes that while a container vessel can speed up quickly, tankers are slower.

Either way, the Sirius Star incident illustrates the pirates' expanded reach using sophisticated global positioning technology and satellite phones. Shippers say they need to remain abreast of any change in pirates' operating patterns. "We have to watch how they adapt," said Navig8's Mirchandani.

Looking ahead, Eurasia's de Pontet said piracy could lessen in coming months if Islamist insurgents take control of the Somali capital, Mogadishu, or if the Islamists and the transitional government finalize a power-sharing agreement.