The Indian navy says it's captured 20 pirates in the Gulf of Aden.
One report says the pirates were attacking a merchant vessel.
The navy responded to a mayday call from MV Gibe, flying under the Ethiopian flag.
The Indian government said in a statement that the captured pirates had a cache of arms and equipment, including seven AK-47 assault rifles, three machine guns, and a rocket-propelled grenade launcher.
Last month, India's navy said it had sunk a pirate "mother vessel" off Somalia.
The BBC reports it later emerged that the vessel was actually a Thai fishing trawler that had been seized by pirates off Yemen.
India is among several countries which have sent warships to the waters off the Horn of Africa amid international concern about piracy there.
Meanwhile, a Greek chemical tanker seized in October has been released, but three crew members are feared dead.
A Kenyan maritime official says the MT Action was released and is limping to safe waters. It's not clear whether any ransom was paid.
Other captured vessels include a Saudi supertanker carrying $US100 million of crude oil, the Sirius Star, and a Ukrainian cargo ship carrying some 30 Soviet-era tanks, the MV Faina.
A regional security conference is being held in Bahrain to discuss the piracy issue.
US Defence Secretary Robert Gates said on Saturday that land-based operations against them are not possible unless there is better intelligence about the pirates.
The US delegation at the United Nations has circulated a draft resolution that would give countries the right to pursue pirates on land as well as at sea.
On Friday, Vice Admiral Bill Gortney, who commands the US Navy's Fifth Fleet in Bahrain, also expressed concern about the difficulty in identifying the pirates.
He said shipping companies should use armed security guards much more to protect their vessels in the Arabian Sea and Indian Ocean.