CNN  — 

The woman detained under suspicion of carrying out the deadly bomb blast in Istanbul on Sunday is a Syrian national who was trained by Kurdish militants, according to Turkish authorities.

Turkish police said in a statement that the suspect entered the country through the city of Afrin in northern Syria without documentation to carry out the attack in the heart of Turkey’s largest city, which killed at least six people and injured more than 80 others.

Officers scanned 1,200 security cameras to determine the route of the suspected attacker, who is alleged to have planted the bomb at the scene before leaving in a taxi, according to the statement. Some 46 people were detained, the police added.

Turkey’s Interior Minister Suleyman Soylu said earlier the government believed Kurdish separatists from the Kurdistan Worker’s Party (PKK) and the Democratic Union Party (PYD) were most likely responsible for the assault, a claim denied by the PKK’s armed wing.

People pay tribute to the victims of Sunday's blast on Istiklal Street, central Istanbul.

“It is PKK/PYD terrorist organization according to our preliminary findings,” Soylu said in a press conference at the scene of the attack on Istiklal Avenue. He did not elaborate or provide details of how investigators had reached this conclusion.

The police added: “In her interrogation, the person stated that she was trained as a special intelligence officer by the PKK/PYD/YPG terrorist organization and that she entered our country illegally through Afrin for this attack.”

The People’s Defense Forces (HPG), the armed wing of the PKK, denied involvement in Sunday’s explosion, according to a statement from the group carried by pro-PKK outlet Agence News Firat (ANF).

“We offer our condolences to the relatives of the victims and wish the injured a speedy recovery. We have nothing to do with this incident,” the group said, according to ANF.

A spokesperson for the armed Kurdish People’s Protection Units (YPG) and the General Commander of the Syrian Democratic Forces (SDF), Mazloum Abdi, also denied involvement in Sunday’s attack. The US-allied SDF is the official defense force of the Autonomous Administration of North and East Syria and its armed forces are led by the YPG.

Turkey’s conflict with Kurdish separatist groups has spanned four decades and claimed tens of thousands of lives. The PKK, which seeks an independent state in Turkey, has been designated a terrorist organization by Turkey, the United States and the European Union.

Interior Minister Suleyman Soylu said the government believed Kurdish militant groups were likely responsible for the attack, a claim the armed camp of the PKK has rebuffed.

Security camera footage of Sunday’s incident shows a woman sitting on a bench for more than 40 minutes and then getting up one or two minutes before the explosion, leaving a bag or plastic bag behind, Turkish Justice Minister Bekir Bozdag told the A Haber news channel on Sunday.

The explosive TNT was detected on citizens who lost their lives, on the vehicle that the suspect used and at the crime scene, according to chemical analysis conducted by police.

The blast happened on Istiklal Street in Beyoglu Square, Istanbul Governor Ali Yerlikaya said.

“We wish God’s mercy on those who lost their lives and a speedy recovery to the injured,” Yerlikaya tweeted.

The six people killed include Yusuf Meydan, a member of Turkey’s Ministry of Family and Social Services, and his daughter Ecrin, according to Derya Yanık, the minister of the agency.

Soylu told reporters Monday that 50 of the 81 people injured have been discharged from the hospital, with 31 people still being treated.

‘What looked like the aftermath of a war zone’

Witness Tariq Keblaoui said he was shopping on Istiklal Street when the explosion happened about 10 meters (32.8 feet) ahead of him.

“People were scattering immediately,” said Keblaoui, a Lebanese-based journalist who was on his last day of vacation in the city.

“Very shortly after, I could see how many injured were on the ground,” Keblaoui told CNN. He says he saw dead bodies and victims who were seriously injured.

Tariq Keblaoui, who witnessed the attack, likened the blast to "the aftermath of a warzone."

“There was a man in the store bleeding from his ears and his legs, and his friends were crying near him,” Keblaoui said.

Istiklal Street was packed with visitors when the blast happened Sunday afternoon, he said.

“It went very quickly from a very peaceful Sunday with a very crowded street full of tourists to being what looked like the aftermath of a war zone,” Keblaoui said.

The explosive TNT was detected at the crime scene, according to Turkish police.

Global leaders united in condemning the attack.

NATO Secretary General Jens Stoltenberg tweeted his “deepest condolences” to the Turkish people, while French President Emmanuel Macron said: “To the Turks: we share your pain. We stand with you in the fight against terrorism.”

Ukrainian President Volodymyr Zelensky tweeted of his “deep sadness” at the news of the blast. “I offer my condolences to the families of those who lost their lives and wish a speedy recovery to the injured,” Zelensky said. “The pain of the friendly Turkish people is our pain.”

Coffins of the victims are carried during a funeral ceremony on Monday.

The United States “strongly condemns the act of violence that took place today in Istanbul,” White House Press Secretary Karine Jean-Pierre said Sunday. “Our thoughts are with those who were injured and our deepest condolences go to those who lost loved ones.”

Soylu rejected the message of condolence from the White House regarding the attack, saying, “Our alliance with a country Whose Senate sends funds to this mentality that provides funds for Kobani and other terror areas and aims to disrupt the peace in Turkey should be questioned. That much is clear.”

CNN has reached out to the US State Department for comment on Soylu’s remarks.

CNN’s Jorge Engels, Sharon Braithwaite, Hira Humayun, Gul Tuysuz, Brice Laine and Hamdi Alkhshali contributed to this report.