Details added (first version posted on 20:17)

One person has been killed and six injured in an explosion near the subway in the Bayrampasa district of Istanbul, the Turkish HaberTurk reported Dec.1.

Social media users have posted various photos of people evacuating the subway station, while local media said that trains have been stopped at one of the stations.

The Turkish NTV channel also reported that the explosion may have been caused by a bomb on an overpass. According to other reports, the explosion was caused by a power transformer blowing up.

The explosion was heard in several districts of Istanbul, residents of the city tweeted. Local media reported that fire services and ambulances were sent to the site of the incident.

Electricity was cut off in Bayrampasa and the surrounding district.

The causes of the incident are not yet clear, Istanbul's subway officials told the media.