Turkish policemen try to secure the area after a strong explosion of unknown origin shook the busy shopping street of Istiklal in Istanbul, on November 13, 2022. - Istanbul governor Ali Yerlikaya tweeted that four people died and 38 were wounded according to preliminary information. (AFP)

Security and ambulances at the scene after an explosion on Istanbul's popular pedestrian Istiklal Avenue, Sunday, Nov. 13, 2022. An explosion on one of Istanbul's most popular pedestrian thoroughfares killed four people and injured 38 on Sunday, authorities said. The cause of the blast on Istiklal Avenue was not immediately clear. Five prosecutors were assigned to investigate the explosion, state-run Anadolu news agency said.(AP)

Security and ambulances at the scene after an explosion on Istanbul's popular pedestrian Istanbul's popular pedestrian Istiklal Avenue, Sunday, Nov. 13, 2022. An explosion on one of Istanbul's most popular pedestrian thoroughfares killed four people and injured 38 on Sunday, authorities said. The cause of the blast on Istiklal Avenue was not immediately clear. Five prosecutors were assigned to investigate the explosion, state-run Anadolu news agency said.(AP)

Security and ambulances at the scene after an explosion on Istanbul's popular pedestrian Istiklal Avenue, Sunday, Nov. 13, 2022. An explosion on one of Istanbul's most popular pedestrian thoroughfares killed four people and injured more than 30 on Sunday, authorities said. The cause of the blast on Istiklal Avenue was not immediately clear. Five prosecutors were assigned to investigate the explosion, state-run Anadolu news agency said.(AP)

People leave the area after an explosion on Istanbul's popular pedestrian Istiklal Avenue Sunday, Istanbul, Sunday, Nov. 13, 2022. A bomb exploded on a major pedestrian avenue in the heart of Istanbul on Sunday, killing six people, wounding dozens and sending people fleeing as flames rose. (AP)

Security officers at the scene after an explosion on Istanbul's popular pedestrian Istiklal Avenue Sunday, Istanbul, Sunday, Nov. 13, 2022. A bomb exploded on a major pedestrian avenue in the heart of Istanbul on Sunday, killing six people, wounding dozens and sending people fleeing as flames rose. (AP)

People leave the area after an explosion on Istanbul's popular pedestrian Istiklal Avenue Sunday, Istanbul, Sunday, Nov. 13, 2022. A bomb exploded on a major pedestrian avenue in the heart of Istanbul on Sunday, killing six people, wounding dozens and sending people fleeing as flames rose. (AP)

Forensics at the scene after an explosion on Istanbul's popular pedestrian Istiklal Avenue, Sunday, Nov. 13, 2022. An explosion on one of Istanbul's most popular pedestrian thoroughfares killed four people and injured more than 30 on Sunday, authorities said. The cause of the blast on Istiklal Avenue was not immediately clear. Five prosecutors were assigned to investigate the explosion, state-run Anadolu news agency said.(AP)

Security and ambulances at the scene after an explosion on Istanbul's popular pedestrian Istiklal Avenue, Sunday, Nov. 13, 2022. An explosion on one of Istanbul's most popular pedestrian thoroughfares killed four people and injured more than 30 on Sunday, authorities said. The cause of the blast on Istiklal Avenue was not immediately clear. Five prosecutors were assigned to investigate the explosion, state-run Anadolu news agency said.(AP)

People leave the area after an explosion on Istanbul's popular pedestrian Istiklal Avenue Sunday, Istanbul, Sunday, Nov. 13, 2022. A bomb exploded on a major pedestrian avenue in the heart of Istanbul on Sunday, killing six people, wounding dozens and sending people fleeing as flames rose. (AP)

Security and ambulances at the scene after an explosion on Istanbul's popular pedestrian Istiklal Avenue, Sunday, Nov. 13, 2022. An explosion on one of Istanbul's most popular pedestrian thoroughfares killed four people and injured more than 30 on Sunday, authorities said. The cause of the blast on Istiklal Avenue was not immediately clear. Five prosecutors were assigned to investigate the explosion, state-run Anadolu news agency said.(AP Photo/FranciscoSeco)