Interior Minister Suleyman Soylu said the order for the attack on Istiklal Avenue was given in Kobani, a city in northern Syria, where Turkish forces have carried out operations against the Syrian Kurdish YPG militia in recent years.
Soylu added that the bomber had passed through Afrin, another region in northern Syria.
Six Turkish citizens, two members each of three families, were killed in the attack. No group has claimed responsibility.
Television news reports showed images of a person, who appeared to be a woman, leaving a package below a raised flower bed on the historic Istiklal Avenue, a popular spot for shoppers and tourists with a tramline running its length.
Fifty people were discharged from hospital after Sunday’s attack, which sparked concerns that Turkey could be hit with more bombings and attacks, like the series that it suffered between mid-2015 and 2017.
Istanbul has been targeted in the past by Kurdish, Islamist and leftist militants. An offshoot of the Kurdistan Workers Party (PKK) claimed twin bombings outside an Istanbul soccer stadium in December 2016 that killed 38 people and wounded 155.
Of those wounded on Sunday, two of the five people being treated in intensive care were in a critical condition, the Istanbul Governor’s office said. They were among the 31 wounded still in hospital.
ECHOES OF PAST ATTACKS
Hundreds of people fled the avenue after the blast on Sunday, as ambulances and police raced in. The area, in the Beyoglu district of Turkey’s largest city, had been crowded as usual at the weekend.
Video footage obtained by Reuters showed the moment the explosion occurred at 4.13 p.m. (1313 GMT), sending debris into the air and leaving several people lying on the ground, while others stumbled away.
Ankara says the YPG, which Washington has supported in the conflict in Syria, is a wing of the PKK.
Turkey has carried out three incursions in northern Syria against the YPG, including in 2019, seizing hundreds of kilometres of land. President Tayyip Erdogan has said this year that Turkey will again target the YPG.
The PKK has led an insurgency against the Turkish state since 1984 and more than 40,000 people have been killed in clashes. It is considered a terrorist organisation by Turkey, the European Union and the United States.
Condemnations of the attack and condolences for the victims poured in from several countries including the United States, the European Union, Egypt, Ukraine and Greece.
Turkish authorities linked support for the YPG by Washington and others to the blast.
The presidency’s communications director, Fahrettin Altun, said such attacks “are direct and indirect results of the support some countries give to terrorist organisations.”
Soylu likened the U.S. condolences to “the murderer arriving as one of the first at the scene of the crime.”