Jundallah (Soldiers of God) said the bombing was a revenge attack for the hanging last year of people from Iran's Baluch minority that adheres to Sunni Islam, SITE Intelligence said on Monday.
The group also denied that three people hanged by Iran over the bombing on Thursday in the southeastern city of Zahedan were involved in the attack, one of a spate of violent incidents ahead of Iran's June 12 presidential election.
"The resistance movement declares that this operation comes as vengeance for the blood of our martyrs… who were executed last year," Jundallah said, SITE reported.
"The movement warns that any execution of its members will result in severe retaliation."
The Baluch people form a significant part of the population in the southeastern province of Sistan-Baluchestan, which borders Afghanistan and Pakistan and whose capital is Zahedan.
In other unrest in Zahedan, five people were killed in an arson attack on Monday and gunmen on motorbikes fired at a campaign office for President Mahmoud Ahmadinejad last week, wounding two campaign members and a child.
