Turkey has accused a Syrian woman of on a packed Istanbul street that killed six people on Sunday and blamed the banned Kurdistan Workers' Party (PKK) for the attack.
Two girls, aged nine and 15, were among those killed when the bomb exploded shortly after 4 pm local time on , one of Istanbul's busiest streets. More than 80 other people were wounded.
"The person who planted the bomb has been arrested," interior minister said in a statement broadcast by the official Anadolu news agency early Monday.
"According to our findings, the PKK terrorist organisation is responsible."
No hard evidence has yet been provided to support the accusations and no group has claimed responsibility.
The PKK on Monday denied responsibility for the blast, as police detain 46 people in relation to the massacre.
"Our people and the democratic public know closely that we are not related to , that we will not directly target civilians and that we do not accept actions targeting civilians," the group said in a statement published by the Firat news agency.
The PKK, listed as a terrorist group by and its Western allies, has fought a sporadic insurgency with Turkey for Kurdish self-rule in southeastern Turkey since the 1980s.
Police, quoted by private NTV television, claimed the chief suspect is a Syrian woman working for Kurdish militants.
Police footage shared with Turkish media appears to show a young woman in a purple sweatshirt being roughly apprehended in an flat.
Police, cited by NTV, alleged that her name is Alham Albashir and said she was detained at 2:50am. Local media alleged she was a trained PKK intelligence operative, although no further proof was given.
The detention comes amid a growing nationalist backlash against Syrian refugees in the country with political parties blaming them for Turkey's economic crisis.
There has been a sharp rise in racist attacks on Syrian and other refugees while the Turkish government has deported many to Turkey, despite outcry from international organisations.
There has been no claim of responsibility from any party, but the Turkish authorities have been quick to pin blame on Kurdish militants.
"We believe that the order for the attack was given from Kobane," Soylu said, referring to a city in Syria near the Turkish border.
PKK-affiliated Kurdish militants control most of northeastern Syria and in 2015, Kurdish fighters drove Islamic State group militants out of the city.
Turkey's NTV channel also shared surveillance footage of a young woman dressed in trousers and wearing a loose black scarf who ran away into the crowd on Sunday afternoon.
Justice minister Bekir Bozdag told A Haber television that a woman had been sitting on a bench for more than 40 minutes, "then she got up", leaving a bag.
"One or two minutes later, an explosion occurred," he said.
On Monday, all the benches had been removed from Istiklal Avenue, where residents laid red carnations at the scene of the blast, some wiping away tears and others speaking of their fear of further attacks in the run-up to elections next June.
"We need more security!" said Idris Cetinkaya, who works at a nearby hotel and who came to pay his respects.
"The police just searched my bag when I got here, but that's the first time in a year. Millions of people come here, anything could happen at any second!"
Istiklal Avenue was previously targeted during a campaign of nationwide bombings in 2015-16 that were blamed mostly on the Islamic State group and outlawed Kurdish militants, killing nearly 500 people and wounding more than 2,000.
On Sunday, Turkish President Recep Tayyip Erdogan denounced the "vile attack" that had the "smell of terror" shortly after leaving for the G20 summit in the Indonesian resort island of Bali.
Kemal Ozturk, a shopkeeper, is among those who fear another explosion ahead of presidential and legislative elections in seven months' time.
"In [the] election period it can happen. It can happen here or in any city," the 42-year-old told AFP. "We live with fear".
Regularly targeted by Turkish military operations, the PKK has also been at the heart of a tussle between Sweden and Turkey, which has blocked Stockholm's bid to join NATO since May, accusing it of leniency towards the group.
International condemnation flooded in from across the world, including from the United States, but on Monday Turkey said it rejected US condolences over the attack.