A sound bomb exploded in Iran's southeastern city of Zahedan Monday evening but caused no casualties, the official IRNA news agency reported.
The explosion took place at 19:50 local time (1510 GMT) in a main street in Zahedan, capital city of the Sistan-Baluchesta Province bordering Afghanistan and Pakistan.
Provincial Police Commander Nourollah Younesi was quoted as saying that the blast caused no injuries, adding it broke the windows of three cars parked on the road and shattered glasses of houses in a 20-meter area.
The incident is under further investigation by the police and security force in the area, he added.
This is the third bombing case witnessed in Iran within two days.
Four bombs went off consecutively within two hours Sunday morning in Ahvaz, capital city of the oil-rich Khuzestan province bordering Iraq, killing eight and injuring scores.
Several hours later, three explosions also caused by bombs took place one after another in Tehran. One of them was placed around a traffic juncture in eastern part of central Tehran and claimed two lives and wounded three.
The explosions occurred on the threshold of Iran's ninth presidential elections.
Iranian Minister of Information Ali Younessi said on Monday that Iran had found the fatal bombing in Ahvaz was related to some foreign agents, stressing that the explosions could never affect the atmosphere of the elections.
"We have provided for the full security of the voting stations and the people who would attend them to cast their votes," Younessi said.