The Latest on Turkish explosion (all times local):

11:50 a.m.

The private Dogan news agency says at least three people have been killed in the explosion on a busy pedestrian street in Istanbul. The agency said 10 people were injured and taken to hospitals. News reports say the explosion is believed to be caused by a suicide bomber.

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11:30 a.m.

An explosion on Istanbul's main pedestrian shopping street on Saturday has injured at least two people, Turkish media reports say. The Dogan news agency says the attack is believed to be a suicide bombing and injured at least five people.

The state-run Anadolu Agency reports 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 off-shoot of the outlawed Kurdistan Workers' Party, or PKK.