Kurdish groups have denied involvement in Sunday's explosion in Istanbul that killed six people and wounded dozens more.
The Kurdistan Workers Party (PKK) and Kurdish-led Syrian Democratic Forces (SDF) both said they played no part in the blast on a busy pedestrian avenue in Turkey's largest city.
Nobody has claimed responsibility for what Turkey has condemned as a terrorist attack. Police said on Monday they had detained a Syrian woman with suspected links to Kurdish militants who confessed to planting the bomb.
The Istanbul Police Department said videos from around 1,200 security cameras were reviewed, and raids were carried out at 21 locations. At least 46 other people were also detained for questioning.
A total of six people were killed, and 81 were wounded in Sunday’s explosion on Istiklal Avenue, a popular street lined with shops and restaurants that leads to the iconic Taksim Square.
The suspect allegedly departed the scene in a taxi after leaving TNT-type explosives on the crowded avenue, police said.
Kurdish militants deny involvement
The PKK denied involvement in a statement, saying it did not target civilians. The commander of the Kurdish-led Syrian Democratic Forces, Mazloum Abdi, also denied on Monday Turkish allegations that the SDF was involved.
Turkey has accused the Syrian Kurdish YPG militia (People's Protection Units), the backbone of the US-backed SDF, of responsibility for the blast.
The group maintained that Turkish President Recep Tayyip Erdogan was trying to gather international support for his plans to launch a new incursion into northern Syria ahead of next year’s elections.
Turkish police said the suspect told them during her interrogation that she had been trained as a “special intelligence officer” by the outlawed PKK, as well as the Syrian Kurdish group the Democratic Union Party and its armed wing.
She entered Turkey illegally through the Syrian border town of Afrin, police said.
The authorities had initially arrested more than 20 suspects since the explosion, Turkey’s interior minister Süleyman Soylu said earlier on Monday, adding that initial findings indicated PKK militants were responsible.
The Turkish interior minister also accused Kurdish forces controlling most of northeastern Syria, which Ankara considers terrorists, of being behind the attack. "We believe that the order for the attack was given from Kobane," he added.
Kobane has remained famous for the 2015 battle that enabled Kurdish forces to repel the so-called Islamic State (IS) group.
The city is controlled by the SDF, of which the YPG -- allied to the militant Kurdistan Workers Party (PKK) -- are a major component.
Blast hits busy shopping area
Hours after the explosion on Sunday afternoon, Vice President Fuat Oktay visited the site to give the latest death and injury toll and promised to resolve the matter "very soon".
The area, in the Beyoglu district of Turkey's largest city, had been crowded as usual at the weekend with shoppers, tourists, and families.
Video footage obtained by Reuters showed the moment the explosion occurred at 16.13 local time (14.13 CET), sending debris into the air and leaving several people lying on the ground, while others stumbled away.
Hundreds of people fled the historic Istiklal Avenue after the blast, as ambulances and police raced in.
Authorities later said a government ministry worker and his daughter were among the dead. Five people were in intensive care in hospital, two of them in a critical condition.
Erdogan: 'it smells like terrorism'
Turkish President Recep Tayyip Erdogan called the blast a “treacherous attack” and said its perpetrators would be punished.
"Efforts to defeat Turkey and the Turkish people through terrorism will fail today just as they did yesterday and as they will tomorrow," the president told a news conference before flying to Indonesia for a summit of the Group of 20 leading economies.
"Our people can rest assured that the culprits... will be punished as they deserve," he said, adding that initial information suggested "a woman played a part" in it.
"It would be wrong to say this is undoubtedly a terrorist attack but the initial developments and initial intelligence from my governor is that it smells like terrorism," he added.
Justice Minister Bekir Bozdag was quoted by state-run Anadolu as saying a woman had sat on a bench for more than 40 minutes before leaving minutes before the blast, suggesting a bomb that was timed to explode or was detonated from afar.
The 23-year-old female suspect was arrested in an overnight raid by anti-terror police in the district of Kucukcekmece.
Turkish authorities say they also recovered a large sum of euros and gold coins, as well as a gun and cartridges.
Sunday’s explosion was a shocking reminder of the safety concerns that stalked the Turkish population during years when such attacks were common.
The country was hit by a string of bombings between 2015 and 2017, some by the Islamic State group, others by Kurdish militants who seek increased autonomy or independence.
Twin bombings outside an Istanbul football stadium in December 2016 killed 38 people and wounded 155 others. The attack was claimed by an offshoot of the PKK, which is designated a terrorist group by Turkey, the European Union, and the United States.
Condemnations of the attack and condolences for the victims rolled in from several countries. On Twitter, European Council President Charles Michel sent condolences to victims after the "horrific news".
NATO Secretary General Jens Stoltenberg also sent his "thoughts and deepest condolences to all those affected and to the Turkish people."