A suspect is in custody related to an explosion that killed at least six people and injured at least 81 others in Istanbul on Sunday, Turkey’s interior ministry said early Monday.

The incident has been deemed a terrorist attack, Turkish Vice President Fuat Oktay said Sunday, according to state news agency Anadolu.

“We consider it to be a terrorist act as a result of an attacker, whom we consider to be a woman, detonating the bomb,” Oktay told reporters Sunday.

Turkish officials believe Kurdish separatists from the Kurdistan Worker’s Party (PKK) and the Democratic Union Party (PYD) were most likely behind the deadly suspected bomb attack, the country’s interior minister, Suleyman Soylu, told reporters Monday.

“It is PKK/PYD terrorist organization according to our preliminary findings,” Soylu said in a press conference at the scene of Sunday’s attack on Istiklal Avenue, Istanbul.

Soylu did not elaborate or provide details of how investigators had reached this conclusion.

“A little while ago the person who left the bomb (was) taken under custody by teams of Istanbul Police Department. Before their arrest 21 more people were also taken under custody,” the minister said. “The face of terrorism is bitter, but we will continue this struggle to the end, whatever the cost is.”

CCTV footage 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, according to Turkish Justice Minister Bekir Bozdag.

Bozdag, who made the comments in an interview with privately owned A Haber news channel, said Turkish security forces believe the woman is the suspect, and officials are investigating her.

“There are two possibilities. Either that bag or plastic bag has a mechanism in it, it explodes on its own or someone detonates it from afar. All of these are currently under investigation.” he added.

“The name of the woman is unknown,” he said. “All the recordings and data about the woman are being analyzed.”

The blast happened on Istiklal Street in Beyoglu Square, in the heart of Turkey’s largest city, 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, the interior minister, said Monday that 50 of the 81 people injured have been discharged from the hospital, with 31 people still being treated.

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

“In particular, the insincerity of our so-called allies who seem friendly to us, who either hide terrorists in their own country, or feeds terrorists in the areas they occupy and send them money from their own senates, is obvious,” Soylu said.

“We will give them a response in the near future, to those who caused us this pain in Beyoglu Istiklal Street so they experience more and more pain,” Soylu said.

‘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.

“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.

Countries unite in condemning the attack

News of the explosion led to a torrent of condolences from around the world.

French President Emmanuel Macron, whose own country suffered a deadly terror attack exactly seven years earlier, shared his sympathies for the Turkish people.

“On this day so symbolic for our Nation, while we think of the victims who fell on November 13, 2015, the Turkish people are struck by an attack in their heart, Istanbul,” Macron tweeted Sunday. “To the Turks: we share your pain. We stand with you in the fight against terrorism.”

European Council President Charles Michel shared his condolences after Sunday’s deadly blast.

“Horrific news from Istanbul tonight,” he said. “All our thoughts are with those currently responding and the people of Türkiye at this very distressing time.”

NATO Secretary General Jens Stoltenberg tweeted his “deepest condolences” to the Turkish people, adding that NATO “stands in solidarity with our ally” Turkey.

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.”

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.” (CNN)

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