Somali pirates holding a Saudi supertanker after the largest hijacking in maritime history are asking for a $15 million ransom, an Islamist leader said on Monday.

The pirates had originally been quoted as wanting $25 million to release the Sirius Star, which has $100 million of oil on board as well as 25 crew members from Britain, Poland, Croatia, Saudi Arabia and the Philippines.

But Islamist spokesman Abdirahim Isse Adow, whose men are in the Haradheere area where the ship is being held offshore after its Nov. 15 capture, told Reuters that demand had been reduced.

"Middlemen have given a $15 million ransom figure for the Saudi ship. That is the issue now," Adow told Reuters.

He added that pirates had taken the ship further out to 100 km (62 miles) off the coast of central Somalia after Islamist militia poured into the town in recent days in search of the group behind the audacious strike that has shocked the world.

Adow, who represents the Islamic Courts Union (ICU), says his men are out to confront the pirates and release the Saudi Arabian Sirius Star because it is a "Muslim" ship. But residents say other Islamist militia are intent on getting a cut of any ransom payment.

The capture of the Sirius Star has stirred up the small dusty harbour into a frenzy of activity, witnesses say, with armed men riding backwards and forwards on cars all over town.

The Islamists, who have been fighting the Somali government and its Ethiopian military allies for the last two years, denounce piracy in public. But analysts say some factions are content to take a share of spoils or use pirate gangs to enable weapons deliveries by sea.

Senior Somali government figures are also on the take from piracy, which has generated millions of dollars in ransoms this year, analysts and diplomats in the region say.

The government denies that.

"We are against this act and we shall hunt the ship wherever it sails, and free it," Islamist spokesman Adow said. "It has moved about 100 kilometres far into the sea to escape from us."

Neither the U.S. navy, which is tracking the saga closely along with other international naval vessels in the area, nor the ship's operators have confirmed any ransom demand.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.