Somali pirates who hijacked Saudi oil super-tanker Sirius Star demanded USD 25 million in ransom and set a 10-day deadline amid mounting calls for tougher action on sea bandits.

"We are demanding 25 million dollars from the Saudi owners of the tanker. We do not want long-term discussions to resolve the matter," a pirate who identified himself as Mohamed Said said from the ship, now anchored at the Somali pirate lair of Harardhere.

"The Saudis have 10 days to comply, otherwise we will take action that could be disastrous," Said added, without

elaborating. In a sign of growing international frustration over a situation described by the International Maritime Bureau (IBM) as "out of control," Russia announced it would send more warships to combat piracy in the waters around Somalia.

Admiral Vladimir Vysotsky, the top commander of the Russian navy, made the announcement according to a report by RIA Novosti news agency.

"After the Neustrashimy (Fearless), ships from other fleets of the Russian navy will head to the region," Vysotsky said, referring to a frigate sent to the area in September.

Russia's ambassador to NATO, Dmitry Rogozin, has meanwhile called for an international ground military operation to better combat rampant piracy in the region.

"It's up to the European Union, NATO and others to launch a coastal land operation to eliminate the pirates," Rogozin said on Wednesday, insisting that ‘naval action alone will not be enough to liquidate the threat of piracy’.