One person was killed after an explosion at an Istanbul metro station that was apparently triggered by a power transformer on Tuesday, Turkey's Haberturk TV said.
A municipal official told Reuters that train operations had been suspended at the Bayrampasa metro station after a loud noise was heard.
Dogan news agency reported that many ambulances were heard rushing to the area, which is a residential and industrial neighbourhood on the European side of the city.
Photographs on social media showed what appeared to be dozens of people walking alongside overground train tracks after trains had been halted.
State-run Anadolu Agency said the explosion happened at an overpass near the metro station. Although Istanbul's metro is largely underground, it runs above ground in some places, including around Bayrampasa.