The perpetrators of Wednesday's twin terrorist attacks in the Iranian capital Tehran were all Iranian nationals who joined ISIL in Iraq and Syria before returning home last summer, the Intelligence Ministry has said. 

The first incident happened in the Iranian parliament while the second took place at a mausoleum. 17 people were killed and 52 injured in the two incidents.

Iranian authorities initially said six people carried out the attacks, with four disguising themselves as women to evade security around parliament. A further two reportedly attacked the mausoleum. 

However, an intelligence ministry statement issued on Thursday amended the number of attackers to five. 

"The five known terrorists... after joining ISIL, left the country and participated in crimes carried out by this terrorist group in Mosul and Raqqa," it said.

US President Donald Trump criticized the Iranian government in the wake of the attacks. In a statement, Trump sent condolences to the victims, but also warned that countries that sponsor terrorism "risk falling victim to the evil they promote."

Iran's Foreign Minister Javad Zarif denounced Trump's statement later on Thursday as "repugnant".

Iranian Foreign Minister Javad Zarif calls Trump's statement "repugnant". /Twitter Screenshot

Iran's President Hassan Rouhani spoke with French President Emmanuel Macron on Thursday and vowed to expand cooperation in the fight against terrorism.