MADRID, Spain — Pirates attacked a Spanish fishing vessel Sunday in the Indian Ocean, firing small arms and a rocket-propelled grenade, but private security guards aboard the ship shot back and repelled them, Spain's Defence Ministry said.

The pirates aboard two skiffs chased the Spanish ship, the Ortube Berria, for about 30 minutes before the security guards fended them off, the ministry said in a statement.

None of the ship's crew members were hurt during the attack, about 430 kilometres southwest of the Seychelles Islands, the statement said.

A European Union naval force staging an anti-piracy operation in the Indian Ocean summoned a Portuguese frigate and a patrol plane to the area. It did not call in a Spanish frigate, Canarias, that is part of the EU anti-piracy mission because it was too far away, the ministry said.

The Canarias had overseen the Nov. 17 release of the Spanish tuna trawler Alakrana after a $3.3 million ransom was allegedly paid to pirates who had held the ship and its 36-member crew for 47 days.