Gardai have searched up to 80 premises across the State in a crackdown on child pornography.
"Operation Amethyst" - set up under Section 7 of the Child Trafficking and Pornography Act, 1998 - began at 6 a.m. and involves 500 officers.
A Garda spokeswoman said no arrests had been made so far but that computer hardware and software had been seized.
A spokesman would not disclose where the searches had taken place, but it is believed at least 50 premises were targeted in Dublin and Cork, with possible operations also under way in Galway and Sligo.
A Garda statement said: "A number of searches have taken place. The operation is still ongoing, material has been seized, for example computer hardware and software.
"An operation room has been set up at the National Bureau of Criminal Investigation. This investigation has been ongoing for a number of months as part of a world-wide investigation into child pornography."
