At least one police officer was killed and seven people wounded in a suicide bombing apparently targeting a police station in central Istanbul.
The suicide bomber set off his explosives after throwing a grenade into the entrance of the police station in the Sultangazi district.
The attacker, identified as a 25 year-old male, was also killed in the explosion, which also lightly injured three civilians, Istanbul police chief Huseyin Capkin said.
Separatist Kurdish militants, far-left groups and Islamic radicals have all carried out attacks in Istanbul in the past. However, no one has, so far, claimed responsibility for the suicide bombing.
The neighbourhood, predominantly populated by Turkey's Alawite minority, was home to mass demonstrations in 1995 after 23 people were killed in four days of rioting with police.
In May, two suicide bombers killed a police officer when they drove into a police station in the central city of Kayseri and opened fire before setting off a bomb. The outlawed Kurdistan Workers Party (PKK), which poses the main domestic security threat in Turkey, said it had carried out that attack.
This summer has seen some of the fiercest fighting between PKK militants and the security forces since the separatist rebels took up arms in 1984 with the aim of carving out their own state in the southeast.
The clashes, which have involved air strikes on Kurdish militants in northern Iraq, have taken place hundreds of kilometres away from Istanbul in the mountainous border region with Iraq and Syria.
Another suicide bombing took place last October in the eastern town of Bingol, where two people were killed when a woman blew herself up near the headquarters of the governing Justice and Development Party (AKP).
In November 2010, a bomber blew himself up in Istanbul's central Taksim square, wounding 32 people.
The most serious recent attacks in Istanbul occurred in November 2003, when car bombs shattered two synagogues, killing 30 people and wounding 146 in what the authorities said bore the hallmarks of al Qaeda.
Part of the HSBC Bank headquarters was destroyed and the British consulate damaged in two more explosions a week later, which killed a further 32 people.