The men, identified as Ali Karimi, Gholam Koohkan and Khodamorad Lashkarzadeh bring to at least 101 the number of people executed in Iran this year, according to an AFP tally.
Amnesty International, which campaigns against the death penalty, says there were 94 executions in Iran last year.
Capital offences in the Islamic republic include murder, rape, armed robbery, apostasy, blasphemy, serious drug trafficking, repeated sodomy, adultery or prostitution, treason and espionage.