According to Iranian authorities, the arrests were made as security forces stepped up efforts to clamp down on suspected terrorists.
Alavi said that in the last month the intelligence ministry had identified and crushed "a terrorist team" nearly every day but had not publicised it to avoiding spreading fear among the public.
Iran's intelligence minister Mahmoud Alavi said that 43 suspects had been arrested by Satursday night and that operations to identify more "terrorist cells" were under way.
Separately, the head of the judiciary in Fars province said seven people were detained in the southern Larestan area for possible ties to Islamic State, Iran's ISNA news agency reported on Saturday.
DUP leader Arlene Foster to hold talks at No10 with Theresa May
It also said Chancellor of the Exchequer Philip Hammond is pushing her to prioritize jobs and the economy in the Brexit talks. Following talks between May and the DUP on Saturday night, a second statement confirmed that no final deal had been reached.
Larijani further thanked officials of many countries and their parliaments who immediately condemned the terrorist attacks on Tehran and extended condolences to the Iranian nation, adding "Saudis, who organized a generous conference in Riyadh to "isolate" Iran, need to feel ashamed and take notes of the solidarity voiced by so many countries for Iran".
The intelligence ministry said 41 suspects were arrested in Tehran, in the northwestern provinces of Kermanshah and Kurdistan, and in West Azerbaijan, near the borders with Iraq and Turkey.
Press TV quoted Iran's Intelligence Minister Mahmoud Alavi, as saying, in a televised interview on Saturday that the mastermind of terrorist attack on Iran's Parliament and the shrine of Ayatollah Khomeini on June 7 were killed earlier in the day by the intelligence forces.
It described the suspects as "agents of Daesh", an Arabic acronym for the Islamic State group, and said they included "operational teams".
- Theresa May, "cadavre ambulant", toujours en quête de majorité — GB
- Disputing Comey's testimony, Trump says he's ready to testify under oath
- Iran makes more arrests after Tehran attacks
- Iran arrests 7 suspects linked to Tehran attacks
- Rangers target Eduardo Herrera arrives in Glasgow
- Defence minister Fallon says government views on Brexit haven't changed
- Législatives. Sarthe : 19,54 % de participation à midi
- Hamilton wins Canadian GP pole, ties Senna on all-time list
- Trump administration appeals travel ban to Supreme Court
- Qatar rejects intervention in foreign policy: FM