The Naval Service patrol ship LE Niamh has rescued 551 people from a wooden barge off the Libyan coast and is en route to the Siclian port of Trapani.
The patrol ship was tasked by the Italian Marine Rescue Co-ordination Centre to investigate the sighting of a possible migrant vessel on Wednesday, some 55 km north of the Libyan port of Zuwarah.
It deployed two rigid inflatable boats to investigate a vessel, described as a fishing boat, with about 700 people on board.
The Italian MRCC tasked another four vessels to help the Naval patrol ship in the complex rescue.
The LE Niamh took 394 men, 96 women and 71 children on the ship and gave food, water and medical assistance where required.
It brings to almost 2,500 the number of people rescued by the Irish ship over the past few months.
Also on Wednesday the Swedish ship Poseidon, which is working with the EU border control agency Frontex, found the bodies of about 50 migrants in the hold of a vessel off the coast of Libya.
During the operation around 430 migrants were saved.
