Turkey's government blamed Kurdish militants on Monday for a blast that killed six people in Istanbul's main shopping street, and said police had detained 22 suspects, including the person suspected to have planted the bomb.
State broadcaster TRT released footage of police escorting a woman, the main suspect, from an apartment after an overnight raid.
Interior Minister Suleyman Soylu said the Kurdistan Workers Party (PKK) and the Syrian Kurdish YPG militia, which Ankara says is a wing of the PKK, were responsible for the attack on the historic and bustling Istiklal Avenue on Sunday.
Soylu said the order was given in Kobani and the bomber passed through Afrin - both cities in northern Syria where Turkish forces have carried out operations against the YPG in recent years.
The woman, with curly hair and in a purple jumper with the words 'New York' on it, was shown being brought into police headquarters in the TRT footage. Police used a dog to search the apartment and found gold, money and ammunition, it showed.
Six Turkish citizens, two members each of three families, were killed in the attack. No group has claimed responsibility.
Hundreds of people fled after the blast on Istiklal Avenue, a popular spot for shoppers and tourists with a tramline running its length. The area, in the Beyoglu district of Turkey's largest city, had been crowded as usual at the weekend.
Earlier television news reports showed images of a person, who appeared to be a woman, leaving a package below a raised flower bed in the middle of the street.
The attack sparked concerns that Turkey could be hit with more incidents ahead of tense elections scheduled for June 2023.
A wave of bombings and other attacks began when a ceasefire between Ankara and the PKK broke down in mid-2015, ahead of a vote in November that year. The last major attack was a shooting at an Istanbul night club on 2017 New Year's Eve.
Istanbul has been attacked in the past by Kurdish, Islamist and leftist militants.
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, while 50 people had been discharged.
ECHOES OF PAST ATTACKS
Video footage obtained by Reuters showed the moment the explosion occurred on Sunday afternoon, sending debris into the air and leaving several people lying on the ground, while others stumbled away.
Turkey has carried out three incursions in northern Syria against the YPG, including in 2019, seizing hundreds of kilometres of land. Earlier this year President Tayyip Erdogan said another operation was imminent.
The United States has supported the YPG in the conflict in Syria, stoking friction with fellow NATO member Turkey.
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."
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.
An offshoot of the PKK claimed twin bombings outside an Istanbul soccer stadium in December 2016 that killed 38 people and wounded 155.