The crew of the LÉ James Joyce have been involved in an operation to rescue almost 2,000 people from 18 separate vessels off the coast of Libya.
The rescue operation began at 8.40am local time today, with 423 of the migrants taken on board the Irish naval vessel by 1.45pm, where they are now receiving food, water and medical treatment.
The operation, which came after a request Italian Maritime Rescue Co-Ordination Centre, took place around 40 nautical miles northwest of the Libyan capital, Tripoli.
A further 1,500 migrants were taken aboard five boats belonging to non-governmental organisations during the same mission.
The rescued migrants will be transferred to a separate vessel this evening to allow the LÉ James Joyce carry out further rescue operations if necessary.
Meanwhile, the European Union has said it will more than double emergency aid to Greece in order to improve living conditions for refugees and migrants who have been stranded in the country for months.
Some €115m in emergency support is being provided by the EU, in addition to €83m earlier this year, the European Commission said.
The money would be channelled via humanitarian organisations towards improving living shelters and access for refugee children to education, while part would be given in cash or voucher schemes, it added.
"The new funding has the key aim of improving conditions for refugees in Greece and make a difference ahead of the upcoming winter," Humanitarian Aid Commissioner Christos Stylianides said.
Just under 60,000 refugees and migrants are stuck in Greece after their attempts to head to central and northern Europe were prevented by a cascade of border shutdowns throughout the Balkans at the start of the year.
Many are accommodated in abandoned army camps or factories. The EU's emergency support aid is in addition to financial support given under other funding programmes.