TEHRAN — The Iranian authorities arrested 41 people Friday in connection with the twin terrorist attacks in Tehran this week, the semiofficial Fars News Agency reported, as evidence mounted that Iranian Kurds affiliated with the Islamic State had carried out the assault.

The men who made their way through the Parliament building on Wednesday, shooting assault rifles, throwing grenades and searching for a way into the main hall, were probably Iranian Kurds, security sources say, though only one has been identified. One of the two assailants at a shrine is understood to be an Iranian Kurd, the security sources said.

The Ministry of Intelligence identified one gunman, Serias Sadeghi, as an Iranian Kurd from the city of Paveh in the country’s west near the Iraqi border. In 2014, the Democratic Party of Kurdistan Iran, an opposition party, published a report about increasing Islamic State activities in Iranian Kurdistan that singled him out as a prominent recruiter who, at times, held sessions in a local mosque.

One website, KhabarDena.Ir, on Friday quoted Mamusta Molla Ghader Ghaderi, a community leader from Paveh, as saying that some of the attackers were from there.