LONDON (Reuters) — Somali pirates are shifting their focus towards the Indian Ocean as foreign navies operating in the Gulf of Aden become more successful in targeting the gangs, a senior shipping industry figure said.

Somali pirate gangs have caused havoc in the waterways linking Europe with Asia this year and have made millions of dollars in ransom payments.

Per Gullestrup, president and chief executive of Clipper Projects, a unit of Danish ship-owning group Clipper, which had one of its vessels hijacked in 2008, said the pirates were adapting their tactics.

"The pirates are obviously changing their hunting grounds and they are moving east of Africa, which we saw earlier this year," he told Reuters in an interview. "That is a high risk area now."

"They are going closer to the Seychelles and that means that of course it is a very vast area and it would be almost impossible to make a secure zone," he said on the sidelines of a piracy conference in London.

Somali pirates, who hijacked a Chinese bulk carrier far off the African coast in the Indian Ocean this week, threatened to execute its 25 Chinese crew members if any rescue was attempted.

"Pirates are increasingly violent and confident and are likely to be more so," Giles Noakes, chief maritime security officer with ship industry group BIMCO, told the conference.

"This is a current, worrying trend," he said.

Foreign navies have been deployed off the Gulf of Aden since the turn of the year and have operated convoys as well as setting up and monitoring a transit corridor for ships to pass through vulnerable points. But their forces have been stretched over the vast expanses of water which include the Indian Ocean, leaving vessels open to attack.

"It seems now there are reports that they are trying to attack at night in the Gulf of Aden which we have not seen before," Gullestrup said.

Earlier this year Clipper paid a $1.7 million ransom to Somali pirates to free the crew and its vessel, the CEC Future, which had been held for 71 days, he said.

Gullestrup said around four to eight of its ships transited the Gulf of Aden each month and the company had placed razor wire along the vessels' deck railings to deter boarding attempts by pirates.

He said re-routing ships around the Cape of Good Hope was not feasible because of the costs involved.

"In the Gulf of Aden if you are a prudent ship owner and you take all the measures ... and you use the convoy system or the transit system, I think your chances of being hijacked are very very low," he said.