According to the Iranian judiciary's Mizan News Agency, the men were sentenced to death in connection with "unrest" in the city of Mashad in northeastern Iran.
One of them was accused by the Islamist regime of being a leader among the protesters; the other two were accused of being involved in the killing of a member of the Iranian security forces.
They were hanged at dawn on Sunday, according to the US-based activist group Human Rights Activists News Agency.
The Norwegian independent human rights organization Iran Human Rights describes them as political prisoners who were convicted in unfair trials.
Human rights organizations accuse Iran of using the death penalty as a tool to instill fear in the population.
