In light of recent terror attacks in Turkey, Iran's embassy in Ankara has requested its citizens to be mindful of their security precautions and follow the security instructions issued by Turkish officials, ISNA news agency reported.
A man leaves an olive branch at the site of an explosion, in Istanbul, Sunday, March 20, 2016. "So far, five people were detained regarding this matter".
"I wish God's mercy on your deceased citizen who lost his life during this abominable attack and offer my sincerest condolences on behalf of my nation and myself to friendly Iranian nation, and primarily to his family and relatives; I wish the injured a speedy recovery", the president added.
He reportedly spent two years in Syria before returning to Turkey illegally.
Police helicopters were circling overhead, and television footage showed people running from the area.
Skin, the lead singer of British band Skunk Anasie, said she was in a hotel overlooking the street at the time of the blast and described the building "shaking like paper".
The release came after Saturday's blast in Istanbul, in which a bomber detonated his explosives on Istiklal street, leaving five people dead and at least 39 others wounded.
A high profile football match in Istanbul was called off and the stadium evacuated two hours before kick-off on Sunday with the Turkish authorities citing an unspecified threat. Responsibility for the past two attacks, both suicide vehicle bombings in the capital Ankara, was claimed by a PKK offshoot.
While Turkey classifies Islamic State as a terrorist group, it was late to seal its borders to jihadists crossing from Turkey into Syria, identifying Kurdish militants and the regime of Syrian President Bashar al-Assad as the primary threats to its national security.
Malaysian tourist Puteh Ismail, 69, told of the horror of the Istanbul attack, which occurred near where she was shopping with her daughter Raszatol Ishak, 44.
Mr Ala said Ankara was determined to continue its fight against extremists but admitted they were struggling to prevent suicide attacks. "We are in close touch with Turkish authorities and reaffirm our commitment to work together with Turkey to confront the evil of terrorism".