A bomb hidden in a box and left in Enghelab Square west of Tehran exploded Sunday, killing one person and injuring two others, the Central Committee of the Revolutionary Guards said.
Authorities said the bomb exploded when a passerby tried to pick up the box and move it.
The man holding the box was killed and two people nearby were injured, authorities said.
No arrests were made, and there were no clues as to who planted the explosives, the spokesman said.
In Paris, members of the Mojahideen Khalq, the guerrilla group opposed to the Ayatollah Khomeini, charged the daughter and son-in-law of a member of parliament had been arrested and possibly executed two weeks ago in Tehran.
The People's Mojahideen Organization of Iran said the Khomeini regime has refused to disclose what happened to two of its members, Mariam Golzadeh-Ghafouri, 20, and her husband, Ali Samadi, 25.
The woman is the daughter of Ayatollah Ali Golzadeh-Ghafouri, a member of the Iranian Majlis, or parliament, who is reported to have been in hiding since the June 1981 crackdown on dissidents.
Golzadeh-Ghafouri's two sons, also members of the Mojahideen, were arrested and killed by the regime last year, the Mojahideen group said.