Speaking to reporters, Guterres Spokesman Stephane Dujarric said the UN chief has strongly condemned the terrorist attacks in Tehran and called for those responsible to be brought to justice.
"All countries must work together in fighting terrorism while upholding the universal rights and values that bind the global community."
The spokesman said Guterres extends "sincere condolences" to the government of Iran and the families of those killed, and wishes a speedy recovery to the injured.
The Wednesday terrorist attack on the Iranian Parliament finished after all four gunmen were killed in confrontation with Iranian security forces.
In another attack on the same day, a group of terrorists opened fire at several people in the mausoleum of Imam Khomeini, the late founder of the Islamic Republic, south of Tehran.
According to officials, 12 people have been martyred and 42 others were wounded in the twin attacks.