New Delhi: Indian naval frigate ‘INS Tabar’ sank a pirate vessel after repulsing an attack in the Gulf of Aden in a significant blow to the sea brigands on Tuesday. The operation comes a week after it saved two merchant vessels—one from India and the other from Saudi Arabia—from being hijacked on 11 November.

Rough waters: A 17 November photo of a Chinese fishing vessel FV Tian Yu 8 , hijacked by pirates, as it passes through the Indian Ocean. The ship was attacked on 16 November. Reuters

Pirates have demanded ransom for another oil-laden Saudi supertanker amid reports that three other merchant vessels have been hijacked.

“Negotiators are onboard the ship and on land," a man identifying himself as Farah Abd Jameh, a member of the group that hijacked the Saudi tanker, said in an audio tape aired by Dubai-based Al Jazeera television. “Once they agree on the ransom, it will be taken in cash to the oil tanker."

Saudi Arabia’s state-owned shipping line, Vela International Marine Ltd, on Tuesday said it had begun negotiating to free the tanker, ‘Sirius Star’, and its crew of 25, seized on 15 November about 420 nautical miles off Somalia. The vessel is carrying at least 2 million barrels of crude valued at $110 million (Rs5,467 crore).

Since January, at least 91 vessels have been attacked in the Gulf of Aden, which is flanked by Yemen on one side and Somalia on the other and leads to the Suez Canal. Ransom payments have spurred raiders to step up their activities, the International Maritime Bureau says.

On Wednesday, pirates released a Hong Kong-flagged ship and its crew held two months ago. ‘MV Great Creation’ was seized on 18 September.

(Bloomberg and AFP contributed to this story.)