The Iranian authorities say the members of the Tawhid and Jihad group were involved in 24 armed attacks between 2009 and 2011.
Iran has executed 20 prisoners for suspected attacks on security forces and committing several murders, state media reported on Thursday.
"These people had committed murders... killed women and children, caused destructions and acted against the security and killed Sunni religious leaders in some Kurdish regions," IRIB television quoted Prosecutor General Mohammad Javad Montazeri as saying.
State news agency IRNA said members of the Tawhid and Jihad group were executed on Tuesday. Iran's intelligence ministry on Wednesday issued a statement detailing 24 armed attacks between 2009 and 2011, including bombings and robberies, apparently by a single group.
The ministry said the group was responsible for the deaths of 21 people in three western provinces in that time span, the ministry said.
"102 members and followers of the Tawhid and Jihad terrorist group were identified... some of whom were killed in armed clashes with police forces and some were arrested. Some of those arrested were sentenced to death while some received prison terms," it added.
In 2009, Tawhid and Jihad allegedly killed two Sunni religious leaders Mamusta Borhan Aali and Mamusta Mohammad Sheikh al Islam -- a provincial representative of Iran's powerful Assembly of Experts.
Iran's judiciary said the latest cases had been under deliberation for more than six years to make sure all aspects were investigated and the rights of the accused were protected
This militant group in Iran's border regions is said to have originated either from foreign fighters who crossed to Iran to fight the Soviet Union in Afghanistan in 1979, or from the presence of Abu Musab Al Zarqawi, who sought refuge in Iran in 2001 or 2002, and went on to found Al Qaeda in Iraq.