The official Iranian news agency IRNA says three men convicted of bombing an Iranian mosque two days ago have been publicly executed.
The bombing killed at least 19 people during evening prayers in the south-east city of Zahedan on Thursday.
The three men, who were hanged on Saturday morning near the mosque, were already in custody before the attack.
One Iranian official had earlier accused the US of hiring mercenaries to carry out the bombing but this was dismissed by Washington.
Authorities said the men were tried and had legal representation.