Seven people are still being held in connection with internet pornography following a series of police raids across Northern Ireland.
The arrests on Tuesday were part of an ongoing investigation into the possession and production of indecent images of children on the internet.
A quantity of computer hard drives and other materials were seized and are being examined by detectives.
A police spokesman said a "significant" number of premises had been searched.
Those arrested are being held at Antrim PSNI station.
In a statement, the PSNI said it was "committed to protecting children from sex offenders who use the internet".
It added the operation was a result of a "close working relationship" with the Child Exploitation and Online Protection Centre, part of the new Serious and Organised Crime Agency in the UK.