Explosion hits a busy shopping street in Turkish city Istanbul

An explosion has hit a busy pedestrian street in the Turkish city of Istanbul, Turkish state-run media is reporting.

The Anadolu Agency reports the explosion happened on Istanbul's central Istiklal Street - a popular shopping area - in the Beyoglu district.

The number of casualties has not yet been officially confirmed. 

Photos on Twitter appeared to show wreckage and people lying on the floor severely injured in the street. Ambulances and police are on the scene.

CNN Turkey posted the first images of the aftermath of the explosion:

The explosion follows two recent suicide bomb attacks in Ankara, the capital of Turkey, which were claimed by Kuridsh militant group TAK.

More to follow.