Five poeple were injured when a pipe bomb exploded on an overpass near Bayrampasa metro station in Istanbul, Turkey.
The explosion took place during rush hour on Tuesday, resulting in suspension of train services to the station.
Bayrampasa is a residential and industrial area located on the European side of Istanbul. The city’s metro network is largely underground, while it runs above ground in some places, including Bayrampasa.
CCTV footage showed large sparks shooting out from the overpass as a train passed near the station.
Bayrampasa district mayor Atilla Aydiner told A-Haber television: "Five of our citizens were injured when a pipe bomb left on barriers on the overpass exploded."
Earlier media reports speculated that the explosion was caused by a power transformer.
Istanbul Governor Vasip Sahin was quoted by Anadolu as saying: "The cause of the explosion is not clear. We are investigating all possibilities.
"It was a large explosion, right in a central location and in a busy place but fortunately there was no loss of life."
Over the past few months, Turkey has been on alert after 103 people were killed on 10 October when two suicide bombers targeted a march of pro-Kurdish peace activists in Ankara.
According to reports, the blast near Bayrampasa metro station was much smaller than the ones in Ankara and the town of Suruc near the Syrian border, which are believed to have been carried out by Islamic State militants.