An explosion on Istanbul's main pedestrian shopping street has killed at least five people and injured 20 others, Istanbul's governor said on Saturday.
The explosion is believed to have been caused by a suicide bombing, according to local news reports.
The state-run Anadolu Agency reported that ambulances were responding to the explosion on Istiklal Street, which is also home to cafes, restaurants and foreign consulate buildings. Private NTV television said the explosion occurred outside a shopping mall.
The explosion comes as Turkey is on edge following two recent suicide bomb attacks in the capital, Ankara, which were claimed by a Kurdish militant group that is an offshoot of the outlawed Kurdistan Workers' Party, or PKK.
Turkey had heightened security in Ankara and Istanbul in the run up to a Kurdish spring festival on 21 March.