The incident occurred almost 1000km off the Somalia coast - north of the Seychelles.

The ship, which has a capacity of 1,500 passengers and crew, was slightly damaged by firing from the pirates, Pinto said.

"They tried to put up a ladder with hooks. They were climbing up, so we reacted. We started firing.

"When they saw us firing - we even sprayed them with water with the fire hose - they gave up and went off."

There were no reports of any major injuries among the ship's crew or passengers, who remained inside the cabin during the attack, Pinto said.

Vessel seized

In a separate incident on Sunday, two Somali pirates were killed after a group of pirates attempted to seize an empty Yemeni oil tanker in the Gulf of Aden, the Reuters news agency reported.

Three pirates and two Yemeni coast guards were also wounded as Yemeni authorities tried to free the vessel, government officials said.

The tanker can carry 3,000 tonnes, but was not carrying any cargo when it was seized off the coast of the Arabian Peninsula country, the official told Reuters.

Pirates have seized dozens of ships in the Indian Ocean, many of which have been released after their owners paid tens of millions of dollars in ransoms.