According to human rights groups, similar confessions by Iranian political prisoners are almost always obtained under duress.
Iran said last week that Iraq had freed three Iranian prisoners, the first such release in two years.
The reporters were also shown hundreds of Iranian prisoners.
Taliban officials have acknowledged that they still hold at least 45 Iranian prisoners.
The Iraqis' treatment of Iranian prisoners throughout the war received little attention in the West.
Iraq holds only about 10,000 to 12,000 Iranian prisoners.
The two organizations produce reports on the situation of Iranian prisoners and gather data about death penalty cases in Iran.
Iraq indicated Saturday that its latest offensive was designed in part to capture more Iranian prisoners.
Iran holds about 40,000 Iraqis, compared to only 15,000 Iranian prisoners held by Iraq.
The campaign calls for an end to mistreatment of Iranian prisoners including Tavakoli.