The LE Niamh is on the way to Sicily with 513 people who were rescued from the Mediterranean today.
The Irish naval vessel rescued 380 people in three operations and also picked up 113 other people who were rescued by an Italian vessel.
The refugees were picked up off the Libyan coast in small boats, and are being given water, food and medical assistance.
Meanwhile, the Hungarian government is criticising a move by Croatia to divert refugees towards Hungary and Slovenia.
European heads of state are preparing for an emergency refugee summit next week.