Two of the prisoners were being held at a temporary detention centre in Tehran. The third individual died as he was being released from a prison in the northern town of Tonekabon.
The hard-line daily Qods quoted Mohammad Tourang, a senior police commander in Tehran, as claiming that one of the individuals being held at the detention centre said that he was sick and was taken to a toilet where he committed suicide by hanging himself using a plastic bag he had with him.
Another individual identified only as Mehdi was brought to a detention centre for interrogation but also managed to commit suicide, the police commander claimed.
In Tonekabon, a prisoner identified only as Kourosh fell ill immediately after being released from prison. He was pronounced dead by doctors in Abbass-Abad Hospital.