That came after Mohammad Hossein Zolfaghari, a deputy Interior Minister, told state TV that "law enforcement activities may increase". He did not elaborate. Another attack involving an explosion took place near the Imam Khomeini shrine, Sputnik International reported. Though most Iranians are Shiite, including separatists in Ahvaz, the eastern Baloch region is majority Sunni, although there are no recent census figures available.
The ministry issued a statement on its website with bloody pictures of the men's corpses.
As the parliament attack unfolded, gunmen and suicide bombers also struck outside Khomeini's mausoleum on Tehran's southern outskirts.
Iran is a key backer of Assad amid his country's six year long civil war. The Syrian president spoke to his Iranian counterpart Hassan Rohani by phone on Thursday. In a message posted through its Aamaq News Agency, the IS group claimed its fighters were behind the assaults.
It said a security guard was killed and that one of the attackers was killed by security guards. No one immediately claimed Wednesday's attacks.
Hezbollah is seen as a proxy to Iran in Syria and Lebanon and has aligned itself with Tehran amid mounting regional tensions with Saudi Arabia and other Gulf states.
A body at background left, lies on the ground while police control the scene at the shrine of late Iranian revolutionary founder Ayatollah Khomeini, just outside Tehran, Iran, Wednesday, June 7, 2017. The Clarion Project said the speakers claimed to represent various Iranian Sunni ethnic groups, such as the Baluchis and Ahvazis, and encouraged Iranian Sunnis to join the group. Both governments are 20th century phenomena: the Saudi state dates to 1932 and the present government of Iran dates only to the Islamic Revolution of 1979.
Other Iranian leaders sought to play down the attacks, with supreme leader Ayatollah Ali Khamenei saying: "These firecrackers that happened today will not have the slightest effect on the will of the people".
"Repugnant WH (White House) statement... as Iranians counter terror backed by USA clients", Zarif tweeted.
Iran will be on its guard once more to prevent the likelihood of another attack and stop propaganda and possible recruitment initiatives by the Islamic State from reaching its borders.
The Senate has cleared the way for action on bipartisan legislation that would authorize President Donald Trump to impose new sanctions on Iran.
"We unequivocally condemn terrorism in all its forms and we express our full support for the people and government of Iran, and our honest condolences to the victims' families", the Greek Foreign Ministry said in a statement.
The Daesh (ISIL) terrorist group claimed responsibility for the attacks.