"There were 52 people in all," defence ministry spokesman Captain M. Nambiar told AFP but was unable to specify the numbers of suspected pirates and rescued hostages, nor could he give their nationalities.

All were found on board a Thai fishing vessel that had been hijacked up to six months ago off the coast of Somalia and is thought to have since been used as a floating base to mount attacks on shipping, a ministry statement added.

Mumbai police said they were expecting to interview all those detained when they arrive in the city.

Indian navy and coastguard were sent to hunt the pirates after the crew of a Greek-flagged vessel said they had been attacked some 100 nautical miles west of Kavaratti, off the state of Kerala in southwest India.

Two high-speed skiffs were located in the early hours of Sunday and chased back to the mothership. Coastguard and navy were fired on twice, the statement said.

"The resultant firefight was brief but decisive with the pirates quickly losing any stomach they might have had for a protracted confrontation and hoisting the white flag of surrender," it added.

"A mix of pirates and crew members being held hostage aboard the trawler were collectively recovered."