The blast took place on Thursday, the necktie party on Saturday.
Two others were arrested and are being questioned in connection with the bombing, which took place Thursday in the southeastern city of Zahedan, the news agency said.
The Zahedan prosecutor, Muhammad Marzieh, said the three men were convicted of importing explosives from neighboring countries, taking two hostages in Zahedan, and taking part in a separate bombing against the security forces and the Revolutionary Guards a year ago, the INSA news agency reported.
“They said that they had eight other terrorist operations which they could no longer carry out because of their arrest,” Mr. Marzieh said.
A provincial judiciary official, Ibrahim Hamidi, said the men were arrested a few days before the bombing but all three confessed to providing the explosive, the IRNA news agency reported.
In related "Bomb-bomb-bomb, Bomb-bomb Iran news", The Iconoclast at the New English Review Journal brings us this:
Security personnel defused a homemade bomb found on an aircraft during a domestic flight in Iran late Saturday, Iranian media said, two days after a mosque bombing killed 25 people in the southeast of the country.
The device was defused after the Kish Air aircraft with 131 passengers on board made an emergency landing in the southwestern city of Ahvaz, the semi-official Fars news agency reported.
Fars gave no further details about the incident, which was also reported by other media.
According to the BBC
Plain-clothes security guards, who are believed to travel on every Iranian flight, found it in a toilet.