The suspect involved in Istanbul's terrorist attack in Taksim district was extradited to Türkiye, Interior Minister Süleyman Soylu announced on Tuesday.

Bulgarian officials delivered Hazni Gölge, who helped fugitive suspect Bilal Hassan escape the country after the terror bombing at the border between the two countries after Turkish authorities determined he was in the Balkan country, Interior Minister Soylu said during a TV interview on Tuesday.

"We discussed the issue with (authorities in) Bulgaria. They delivered him (Gölge) to us in Edirne at around 6.00 p.m. (1500GMT). We thank Bulgaria for the cooperation," the minister added.

Hassan had dropped off the perpetrator of the bombing on the day of the attack that killed six people and left 81 injured on Istanbul's busy Istiklal Avenue.

The Istanbul Chief Public Prosecutor's Office's investigation into the terror attack is underway, with 59 suspects taken under custody, 24 of whom are under arrest as part of the investigation.

Soylu had previously announced that Hassan's brother had also been nabbed by security forces.

According to the investigation, Ahlam Albashir, who planted the bomb, confessed that she entered Türkiye illegally from the Syrian city of Afrin after receiving intelligence operative training from the YPG/PKK terrorist group. In its over 40-year terror campaign against Türkiye, the PKK – listed as a terrorist organization by Türkiye, the United States and the European Union – has been responsible for the deaths of over 40,000 people, including women, children and infants. The YPG is the terrorist group's Syrian offshoot.

After the attack, Türkiye launched aerial operations against the terrorist group in Syria and Iraq while President Recep Tayyip Erdoğan implied that a ground operation to clear Syria's north of terrorist groups threatening Türkiye was also on the table.