A suspect has been detained in connection with the explosion that occurred in Istanbul on Sunday, leaving at least 81 people injured and at least six people dead, the Turkish interior minister reported early on Monday.

According to state news agency Anadolu, the incident was deemed a terrorist attack on Sunday by Turkish Vice President Fuat Oktay.

"We believe it to be a terrorist incident since an assailant, who we estimate to be a woman, detonated the explosives," Oktay told reporters on Sunday.

According to Suleyman Soylu, the interior minister of Turkey, Kurdish separatists from the Democratic Union Party (PYD) and the Kurdistan Worker's Party (PKK) are most likely responsible for the deadly alleged bomb attack.

In a press conference held at the scene of the attack on Istanbul's Istiklal Avenue on Sunday, Soylu declared, "According to our first findings, it is PKK/PYD terrorist group."

Soylu didn't elaborate or provide details on how the investigators arrived to this decision.

The person who left the explosive was just apprehended by teams from the Istanbul Police Department. According to the ministry, 21 more people were also taken into custody prior to their arrest. "Terrorism has a bitter face, but no matter what the cost, we will battle it to the bitter end."

CCTV footage allegedly shows a woman sitting on a bench for more than 40 minutes before getting up right before the explosion and leaving a bag or plastic bag behind, according to Turkish Justice Minister Bekir Bozdag.

In an interview with the privately owned A Haber news network, Bozdag claimed that the woman is the subject of an investigation by the government and that Turkish security services believe she is the suspect.

There are two potential outcomes. That bag or plastic bag either has a mechanism, explodes on its own, or is detonated remotely. All of these are being looked into right now, he added.

The woman's name is unknown, he said. "We are analyzing every recording and piece of information we have on the woman."

The explosion happened on Istiklal Street in Beyoglu Square, the heart of Turkey's largest city, according to Istanbul Governor Ali Yerlikaya.

"We wish God's mercy on those who lost their lives and a speedy recovery to the injured," Yerlikaya added.

The six fatalities included Yusuf Meydan and his daughter Ecrin, both workers for Turkey's Ministry of Family and Social Services, according to Derya Yank, the agency's minister.

According to Soylu, the interior minister, 50 of the 81 injured people have been released from the hospital, while 31 others are still receiving medical care.

Tens of thousands of people have died throughout Turkey's four-decade conflict with Kurdish separatist groups. The PKK has been designated as a terrorist organization by Turkey, the US, and the EU.

The insincerity of our so-called allies,' who either feed terrorists in the territories they control and send them money from their senates or hide terrorists in their own countries, is particularly clear, according to Soylu.

In the near future, Soylu promised, "We will respond to those who brought us this grief in Beyoglu Istiklal Street so they suffer even more agony.

"What looked like the ruins of a battle zone"

Tariq Keblaoui, a witness, claimed that the explosion occurred around 10 meters (32.8 feet) ahead of him as he was shopping on Istiklal Street.

Immediately, according to journalist Keblaoui, who is based in Lebanon and was in the city for his final day of vacation.

Very soon after, Keblaoui told CNN, "I could see how many injured were on the ground." He claims to have seen both dead bodies and critically hurt individuals.

A man in the store who was bleeding from his ears and legs was there, and his buddies were sobbing close by, according to Keblaoui.

When the explosion occurred on Sunday afternoon, Istiklal Street was jam-packed with tourists, he claimed.

A fairly tranquil Sunday with a very bustling street full of tourists suddenly changed to what appeared to be the aftermath of a war, according to Keblaoui.

Countries banded together to denounce the attack

As soon as the explosion was reported, condolences poured in from all around the world.

The president of France, Emmanuel Macron, expressed his sympathy for the Turkish people after his nation endured a devastating terror attack precisely seven years earlier.

On November 21, 2015, a man makes his way to Paris' Place de la Republique (Republic Square) carrying red roses in honor of the victims of the November 13 terrorist attacks. 130 people were killed in a coordinated wave of attacks on Parisian clubs that the Islamic State group (IS) militants claimed responsibility for.

"While we remember the victims who died on November 13, 2015, the Turkish people are struck by an attack in their heart, Istanbul," Macron tweeted on Sunday. "On this day so symbolic for our Nation." To the Turks: We feel your suffering. We support your efforts to combat terrorism.

Following Sunday's fatal explosion, Charles Michel, president of the European Council, expressed his condolences.

Terrible news tonight from Istanbul, he remarked. "All our thoughts are with those who are responding and the people of Türkiye at this incredibly terrible time," the statement reads.

NATO Secretary General Jens Stoltenberg tweeted that NATO "stands in solidarity with our friend" Turkey and sent his "deepest condolences" to the Turkish people.

The White House Press Secretary, Karine Jean-Pierre, stated on Sunday that the United States "deeply condemns the act of violence that took place today in Istanbul." "Our hearts go out to those who lost loved ones and our sympathies are with those who were hurt."

Volodymyr Zelensky, the president of Ukraine, stated that the news of the explosion caused him "great sadness." Zelensky added, "I extend my sympathies to the families of those who passed away and hope for a rapid recovery to the injured. "Our pain is the pain of the gracious Turkish people."