Istanbul metro station rocked by 'bomb' blast

A station on the Istanbul metro network has been rocked by a blast suspected to have been caused by a home-made bomb, causing panic in the evening rush hour and wounding a reported five people.

The local mayor and Turkish news reports on Tuesday said the blast hit an overpass close to the metro station in the Bayrampasa district of Istanbul.

"Five of our citizens were injured when a pipe bomb left on barriers on the overpass exploded," Atilla Aydiner, the district mayor, told A Haber television.

Security sources were also quoted by the Dogan news agency as saying the blast appeared to have been caused by a home-made bomb.

The metro system in Turkey's largest city was brought entirely to a halt after the blast, the municipality said, although reports said that normal service was later restored.

Other reports had said the cause of the blast could have been linked to an electrical transformer. Early reports - since retracted - said one person had been killed.

Video footage on Dogan showed large sparks shooting out like fireworks from the overpass, lighting up the sky during the height of evening rush hour.

Dogan also said a truck on the overpass was damaged by the explosion with holes on its windshield while other pictures showed a public bus with blown-out windows. 

Large numbers of ambulances were despatched to the scene, as commuters were helped to safety, reports said.

"The cause of the explosion is not clear. We are investigating all possibilities," Istanbul governor Vasip Sahin was quoted as saying by the state-run Anatolia news agency.

He gave a lower toll of just one person injured.

Turkey is currently on alert for attacks after 103 people were killed on 10 October when two suicide bombers ripped through a crowd of peace activists in the capital Ankara, the worst attack in modern Turkey's history.

Turkey has in recent weeks detained several suspected members of the Islamic State (IS) group with officials saying they were planning attacks in the city.

The Paris attacks on 13 November Paris that left 130 people dead and were claimed by the Islamic State group also raised fears over Istanbul's potential exposure to a similar assault. 

But Turkey is also waging war on the outlawed Kurdistan Workers Party (PKK) who have staged dozens of deadly attacks against members of the security forces but largely in the southeast of the country.

The banned Revolutionary People's Liberation Party–Front (DHKP-C) has also staged a string of usually small-scale attacks in Istanbul over the last months.