An Indian Navy ship has thwarted a pirate attack on a merchant vessel with ten Indian crew members in the Gulf of Aden, in which two of the eight Somali pirates were feared killed and the rest arrested, Navy sources said on Friday.

The attack on the Norwegian-owned merchant vessel -- M V Maud, flying the Liberian flag -- took place about 225 nautical miles east of Aden around one am on Thursday, the sources said.

INS Talwar, a guided missile frigate, was escorting a three-vessel group in the international recommended transit corridor in the Gulf of Aden when the crew of the M V Maud noticed an eight-member pirate gang in a skiff approaching them.

The vessel's captain sent a distress signal to INS Talwar, which rushed a helicopter to ward off the piracy attack.

"There was just about two-mile visibility at that hour due to the haze. And the short distance and high speed of the skiff left INS Talwar with little time to respond," the sources said.

As the helicopter approached the merchant vessel, Navy personnel noticed two of the pirates trying to board the ship after locking a ladder on it. The Navy fired at the two men, who fell into the sea.

"We shot at the two pirates boarding the ship and they fell into the sea. We did not notice them resurfacing. We are not sure about their fate," sources said.

Later, Talwar sent its men in a rigid hull inflated boat to the pirate's skiff. The pirates surrendered to the navy, which disarmed them and dumped their fuel.

The Navy also recovered a large cache of arms that included AK-47 rifles, rocket-propelled grenades, a rocket launcher, ammunition, GPS and mobile phones.

The six men on the skiff, which was adrift, were later picked by another foreign warship, Navy sources said.

"Thursday's incident was by far the most dangerous operation that the Navy has carried out against pirates in the Gulf of Aden, as the pirates were already in the process of boarding the merchant vessel. If they had boarded and taken control of the cargo ship, the curative task would have been more difficult," the sources said.

Since the Navy joined the international anti-piracy operations in the Gulf of Aden last November, it has already busted a pirate mother ship and rescued about half-a-dozen merchant vessels, including those bearing foreign flags.

Manpreet Singh Dhaliwal, the Captain of MV Maud, thanked the Indian Navy. "On behalf of the owners, crew and officers of MV Maud, I wish to express our gratitude for your prompt and effective action to thwart the attempted piracy attack on MV Maud earlier today," he stated in a letter.