A suspected suicide bomber wounded 32 people in an attack targeting Turkish police in Istanbul's main square.
No organisation has claimed responsibility, officials said, though the city has been targeted in the past by Kurdish separatist militants and al Qaeda, as well as militants from Turkey's far-left.
A bomb disposal unit was at the scene, and forensic teams pored over debris scattered over the city's Taksim square, which remained sealed off hours after the blast.
The bomber struck near police buses parked close to a monument commemorating Mustafa Kemal Ataturk, the founder of modern Turkey, in the centre of the square. The police presence in Taksim is raised around national holidays like Republic Day, which was celebrated on Friday.
Of those injured in the attack, only nine were kept in hospital. Most of those were police officers.
Istanbul city has been targeted before by Kurdistan Workers Party (PKK) rebels, but the separatist group extended a unilateral ceasefire last month, and on Saturday said it would announce in the coming days whether it would extend it further. PKK suicide bombers have attacked security forces in the past, but not for many years.
Al Qaeda suicide bombers have carried out a series of attacks in Istanbul and, in recent weeks, Turkish police have made several arrests of people suspected of providing support to al Qaeda militants fighting in Afghanistan.
