Foreign Minister Zarif said terrorism and extremism are global problems and tackling the two threats needs global action involving all nations.
Earlier, Iranian President Hassan Rouhani also "firmly condemned" the terrorist attacks.
Posting a message on his Twitter account, the Iranian president offered his deepest condolences to the Belgian government and people, particularly those who lost their loved ones.
"I firmly condemn terrorist attacks in Brussels. My deepest condolences to the government & people of Belgium, especially those who lost loved ones," he twitted.
At least 36 people were killed and well over 200 others wounded in a series of bomb attacks in the Belgian capital on Tuesday, where ISIS bombers targeted the airport with a pair of suicide blasts, and subsequently bombed a subway train at Maelbeek station, near the EU headquarters.
"I firmly condemn terrorist attacks in Brussels. My deepest condolences to the government & people of Belgium, especially those who lost loved ones, he twitted"
There appear to have been three bombers at the Brussels Airport, two of them killed as suicide bombers, and the other leaving a nail-bomb and leaving the airport. He is still at large, and authorities recovered his bomb, which never detonated.
The deadliest attack came an hour after the airport bombings, however, when a man opened fire in a subway train before detonating, killing over 20 people. Officials say they recovered a Kalashnikov rifle from the scene.
Brussels has been under virtual lockdown since then, with the airport closed, and all public transportation shut down. The Eurostar train system, despite not being targeted, has similarly been shut down in the wake of the attacks.
Several nations have offered travel warnings against going to Brussels since then, and indeed it would be difficult to do so even if one was of a mind to. The fear of more ISIS attacks is spreading far beyond Brussels, however.
Officials reported stepped up security in several major US cities, and travel firms say they believe that summer vacations to all cities in Europe are likely to be down dramatically over last year because of fear about security risks.
With Belgian officials focusing their efforts on the third bomber at the airport, US intelligence officials say they believe there are “more than a handful” of other ISIS figures involved in the attack who are yet to be tracked down.
ISIS was quick to claim credit for the strikes and bragged about more coming, but US officials say there is no credible evidence that any specific threat exists against any particular target in the US, FNA reported.
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