One part of the footage showed a man reclining on the floor and forcing a naked boy to sit on him. The children depicted in the seized videos are believed to be mainly Russian.
The clips were included on a prime time news story concerning the break-up of a major international paedophile ring by Italian police.
The moves followed a stormy parliamentary session in which the country's centre-right opposition called for a wider investigation into RAI's programming.
Italy's Justice Minister Piero Fassino has ordered an inquiry into how the RAI obtained the footage, and whether it had broken the law by transmitting pornographic images during prime-time news.
'Infernal' footage
"In no country in Europe would such footage have been broadcast at 8pm by a state television, and at least not by a serious television," said Guido Podesta from the opposition Forza Italia party.
Michele Bonatesta from the far-right National Alliance called the footage "infernal", amid wider demands from parents' organisations and TV watchdogs for more heads to roll.
The head of the national press federation, Paolo Serventi Longhi, condemned the broadcast, as did the head of state television, Pier Luigi Celli, who called it "incredible".
Despite the initial outrage, the images were rebroadcast on the next newscast, RAI Uno, an hour later.
Violent images
Following the repeat, RAI's news director Gad Lerner, went on the air to apologise to viewers for showing images that were not only "unwatchable, but violent."
One part of the footage showed a man reclining on the floor and forcing a naked boy to sit on him. The children depicted in the seized videos are believed to be mainly Russian.
Police have arrested eight Italians and three Russians so far, but say they have enough evidence to begin investigations into a further 1,700 people.
Investigators say the paedophile ring, which was organised mainly over the internet, specialised in the production and distribution of images showing children, some just 2-years-old being sexually and physically abused.