Nairobi - Somali pirates have demanded a ransom for a Saudi supertanker carrying around 100 million dollars worth of crude oil amid reports Wednesday that another ship had been seized and that an Indian warship had destroyed a pirate vessel.

"Negotiators are on the ship and on land," Farah Abd Jameh, who claimed to be a member of the group that seized the Sirius Star, said in a tape sent to Arabic broadcaster al-Jazeera. "Once they agree on the ransom, it will be taken in cash to the oil tanker."

The Sirius Star, which was hijacked Saturday some 830 kilometres south-east of the Kenyan coastal city of Mombasa, Wednesday remained anchored near the Somali port of Harardhere.

Harardhere is around 400 kilometres from the pirate stronghold of Eyl, where the hijackers often take ships and keep international warships at bay by holding crew members hostage.

Piracy off the coast of Somalia has surged this year. Prior to the latest seizures, the International Maritime Bureau (IMB) said there had been 92 attempts at piracy in the region this year, 36 of them successful.

The tanker's owner Vela International Marine Limited, a subsidiary of Saudi Arabian oil company Saudi Aramco, said the ship was carrying a full load of crude oil when it was seized.

The Sirius Star, which is 332 metres long, can carry up to 2 million barrels of oil.

The ship's 25 crew, who are from Britain, Croatia, the Philippines, Poland and Saudi Arabia, are all safe, Vela International said in a statement on its website.

"Our first and foremost priority is ensuring the safety of the crew," said Salah B Ka'aki, president and chief executive of Vela International.

Authorities in the semi-autonomous Puntland region of Somalia and the US Navy, which operates a security patrol in the Gulf of Aden, told Deutsche Presse-Agentur dpa they do not plan to attempt to free the tanker by force.

Meanwhile, a maritime official said Wednesday that a Greek ship has become the third vessel seized by Somali pirates in the last 24 hours.

Andrew Mwangura of the East African Seafarers' Assistance Programme said he had received reports that a Greek ship was taken along with around 25 crew. There was no information on the ship's name, cargo or destination.

However, the Greek Ministry of Merchant Marine said that it had not recorded any incident of a Greek-owned or Greek-flagged ship being seized.

Noel Choong, head of the IMB's Piracy Reporting Centre, told dpa Wednesday he could not confirm the report either.

Choong said the IMB knew only of the hijacking Tuesday of a Hong Kong-flagged cargo ship and a Kiribati-flagged fishing boat.

The Hong Kong-flagged Delight, with around 25 crew onboard, is operated by the Islamic Republic of Iran Shipping Lines and was carrying wheat to Iran. The Kiribati-flagged fishing boat was operated out of Thailand and had 12 crew onboard.

Both ships were believed to be heading to anchorage off the coast of Somalia.

Despite the successful hijackings, the pirates have also suffered losses.

The Indian navy said Wednesday that its INS Tabar stealth frigate, which has been deployed in the Gulf of Aden for anti-piracy surveillance and patrol operations, destroyed a pirate mothership.

The INS Tabar returned fire on a pirate vessel that threatened it, leading to an explosion that forced two speedboats to abandon the pirate ship.

Last week, the INS Tabar staved off an attack by Somali pirates on two merchant vessels - one from India and another from Saudi Arabia.

The Sirius Star is the largest vessel taken by pirates and represents their most daring raid yet, despite the presence of international warships.

The attack took place outside the normal danger areas in the Gulf of Aden. Choong said this showed that hijackers could be changing their tactics to avoid the warships.

The surge in piracy has prompted increased patrols by the North Atlantic Treaty Organization, Russia, the US-led coalition forces and France along the Somali coast.

The European Union has also authorized a force of between five and seven frigates, which is expected to arrive in the Gulf of Aden early December.

The Gulf of Aden is a relatively narrow and busy shipping channel which forms part of the route linking the Indian Ocean with the Mediterranean Sea through the Suez Canal.

If the latest report of the ship, Greek or not, being hijacked proves correct, 17 vessels are in the hands of pirates along with over 300 crew.

Many of the seamen being held are Filipino. Philippine Foreign Affairs spokesman Claro Cristobal said Wednesday that there were 19 Filipinos aboard the Sirius Star, bringing the total number of Filipino nationals being held to 127.

Amongst the ships being held is Ukrainian freighter, the MV Faina, which was captured while carrying 33 military tanks to Mombasa.

A Japanese-owned ship, Stolt Valor, which had 18 Indian sailors aboard, was freed Sunday, nearly two months after it had been seized, after its shipping company reportedly paid a ransom of 2.5 million dollars. (dpa)