The Indian navy has defended its action in sinking a ship near Somalia that maritime officials have confirmed was a hijacked Thai fishing boat.
The International Maritime Bureau said the Ekawat Nava 5 had been captured by pirates earlier in the day on 18 November and the crew was tied up.
One crewman was found alive after six days adrift but 14 are still missing.
The Indian navy said the ship was a pirate vessel in "description and intent" and had opened fire first.
India is one of several countries currently patrolling the Gulf of Aden, one of the world's busiest shipping lanes, amid increasing attacks by Somali pirates.
Almost 40 ships have been seized this year, the biggest the Saudi oil tanker, Sirius Star, which is still being held off the Somali coast.
Indian navy spokesman, Commander Nirad Sinha, told AFP news agency: "The vessel was similar in description to what was mentioned in various piracy bulletins.
"The Indian navy ship asked them to stop for investigation. On repeated calls, the vessel responded by saying it would blow up the Indian ship," he said.
"Pirates were seen roaming on the deck with rocket-propelled grenade launchers."
Commander Sinha insisted that the INS Tabar only opened fire after being fired upon, and that "exploding ammunition was also seen" on the target.
Noel Choong, who heads the International Maritime Bureau's (IMB) piracy reporting centre in Kuala Lumpur, Malaysia, confirmed the vessel was the Ekawat Nava 5.
"The Indian navy assumed it was a pirate vessel because they may have seen armed pirates on board the boat which had been hijacked earlier," Mr Choong told Associated Press.
"We are saddened with what has happened. It's an unfortunate tragedy. We hope that this incident won't affect the anti-piracy operation by the multi-coalition navies there," he said.
The owner of Ekawat Nava 5, Wicharn Sirichaiekawat, said his company had informed the IMB the boat had been hijacked and had asked for assistance.
The British navy confirmed the boat had been boarded and that any action could harm the crew.
The IMB sent an alert to other multi-coalition patrol vessels but Mr Choong said it was unclear whether the Indian vessel had received it as it had no direct IMB links.
Mr Choong urged more cooperation in the future.
Mr Wicharn said the boat had been headed from Oman to Yemen to deliver fishing equipment when it was approached by the pirates in two speedboats.
The Indian navy mistook the vessel for a pirate "mother ship", he said.
Mr Wicharn said he had learnt the fate of his trawler from a Cambodian crew member who had survived the bombardment and had been rescued by a passing ship after six days adrift in the Indian Ocean.
The sailor was now recovering in a hospital in Yemen, he said.
The survivor said all the crew were tied up except the captain and translator.
Mr Wicharn said the Thai foreign ministry had summoned the Indian ambassador to issue a complaint.