A Spanish navy ship fought off a gun attack by pirates on the Somali coast Thursday, then chased and captured six of the attackers while one was reported killed, authorities said.

The support-and-combat vessel Patino, part of a European Union security mission, early Thursday "suffered an attack by a pirate skiff that led to the detention of six of the attackers," the Spanish defence ministry said.

The pirates opened fire on the Spanish ship, prompting it to respond with "light fire," the ministry said in a statement. When the pirates continued shooting, the ship responded with "neutralisation fire in self-defence".

The ship eventually sent out a helicopter to chase the pirates. The pirates threw their weapons overboard and surrendered when the helicopter caught up with their boat.

"Six pirates have been taken on board the Patino, of which five are injured," the ministry said. "Those detained said that another companion died in the incident and was thrown by them into the sea."

The Patino operates under the EU's Operation Atalanta, a multinational mission to protect ships in the perilous shipping route off the coast of Somalia, where hundreds of seamen have been taken hostage.

The EU force NAVFOR that patrols the region said in a separate statement that the Patino, the flagship of its mission, had been escorting a ship carrying food aid to Somalia for the World Food Programme.

Two of the injured pirates received medical treatment on board the Patino, NAVFOR said, adding that it was looking for signs of the pirate who was reported killed.