Six people were killed and dozens injured when a bomb exploded on a popular pedestrian street in Istanbul on Sunday.
Footage posted online showed ambulances, firefighters and police at the scene on Istiklal Avenue, a usually crowded thoroughfare popular with tourists and locals and lined with shops and restaurants.
In one video, a loud bang could be heard and flames could be seen, as pedestrians turned and fled. Social media users said shops had been closed and the avenue had been closed.
Turkish President Recep Tayyip Erdogan called the blast a “treacherous attack” and said its perpetrators would be punished.
In addition to the six dead, Mr Erdogan said 53 others had been injured, according to information he had received from the governor of Istanbul.
Turkey was hit by a series of deadly bomb attacks between 2015 and 2017 by the so-called Islamic State group and banned Kurdish groups.
Five prosecutors have been assigned to investigate the blast, the state-run Anadolu news agency reported.
Turkey’s media watchdog has imposed temporary restrictions on reporting on the blast – a move that prohibits the use of videos and close-up photos of the blast and its aftermath.
The Supreme Radio and Television Council has imposed similar bans in the past, following attacks and accidents.