Iranian security forces killed the mastermind behind the Wednesday's twin attacks claimed by Daesh.
Iran has arrested almost 50 people in connection with a twin attack on Tehran that killed 17 people last week, officials said, as security forces stepped up efforts to crack down on suspected militants.
Daesh claimed responsibility for the suicide bombings and gun attacks on parliament and the mausoleum of the Islamic Republic's founder, Ayatollah Ruhollah Khomeini, on Wednesday.
Iran's intelligence minister Mahmoud Alavi said on Saturday night that 43 suspects had been arrested and operations to identify and crush more "terrorists cells" were underway.
On Sunday, the head of the justice department in Kordestan province in western Iran announced more arrests.
Iran's intelligence minister said the mastermind behind Wednesday's attacks in Tehran was killed by security forces on Saturday.
"The mastermind and main commander of terrorist attacks on the parliament and Mausoleum of Ayatollah Khomeini was killed today by the security forces," Mahmoud Alavi was quoted as saying by state broadcaster IRIB on Sunday.
Iran's intelligence ministry said on Thursday that five of the gunmen and bombers were Iranian members of Daesh who had fought in the militants' strongholds in Syria and Iraq.
The attacks were the first claimed by Daesh inside the tightly controlled Shi'ite country.The group has long vowed to attack Iran because the country had deployed military advisers and support to both Syria and Iraq in their fights against the extremist group
The militant group's Amaq news agency released a video on Thursday evening showing what it claimed was a message from the Tehran attackers.
The four-minute video showed three masked men sitting on a floor holding automatic rifles.
The speaker claimed to represent the "first battalion" of Daesh formed inside of Iran. He spoke out at length against Shiites and promised further attacks.