ISTANBUL - An Indian warship destroyed a pirate ship in the Gulf of Aden and gunmen from Somalia seized two more vessels despite a large international naval presence off their lawless country.

The buccaneers have taken a Thai fishing boat, a Greek bulk carrier and a Hong Kong-flagged ship heading to Iran since Saturday's spectacular capture of a Saudi supertanker carrying $100 million of oil, the biggest ship hijacked in history.

Meanwhile, the Saudi foreign minister yesterday said the owners of a hijacked oil tanker are negotiating with the pirates that are holding it. Asked if he could confirm reports that a ransom had been demanded, Prince Saud Al-Faisal said the owners of the tanker "are negotiating on the issue," said The Associated Press. "The Saudi government does not like to negotiate with pirates or terrorists but the owners of the tanker are the final arbiter on the issue," he added.

Earlier, Al-Jazeera, the Arabic satellite channel, broadcasted an audio tape that it said was of one of the pirates making a ransom demand. "Negotiators are located on board the ship and on land. Once they have agreed on the ransom, it will be taken in cash to the oil tanker," said the man identified as Farah Abd Jameh, who did not indicate the amount to be paid, reported Agence France Presse.

The explosion of piracy off Somalia this year has driven up insurance costs, made some shipping companies divert around South Africa and prompted an unprecedented military response from NATO, the European Union and others.

"The pirates are sending out a message to the world that 'we can do what we want, we can think the unthinkable, do the unexpected'," Andrew Mwangura, coordinator of the East African Seafarers' Assistance Program, told Reuters in Mombasa.

India's navy said one of its warships, INS Tabar, fought Somali pirates in the Gulf of Aden and destroyed their vessel after a brief battle late on Tuesday.

The International Maritime Bureau said pirates had hijacked a Thai fishing boat with 16 crew. That followed the capture of a Hong Kong-flagged ship carrying grain bound for Iran. Mwangura's group said a Greek bulk carrier had also been seized, but an official at Greek Merchant Marine Ministry in Athens said that no such incident had been recorded.