A suicide bomber blew himself up at a police station in Istanbul Tuesday, killing a Turkish police officer in an Alawite-majority area where deadly unrest erupted almost two decades ago.
There was no immediate claim of responsibility for what was a rare suicide bombing in a country that has nevertheless witnessed numerous attacks by Kurdish rebels as well as Islamists and leftwing extremists.
"The suicide bomber set off the explosives on him after throwing a grenade into the police station, and killed one police officer and wounded four others at the entry," Istanbul police chief Huseyin Capkin told reporters.
The attacker, identified as a 25 year-old male, was killed in the blast, which also wounded three civilians, Capkin said.
Riot police, reinforced by armoured tanks and water cannon, sealed off the area of the attack in Gazi, an Alawite-dominated area in the European sector of Turkey's biggest city.
Police stations in the neighbourhood had been fortified after four days of demonstrations and deadly unrest in 1995 which killed 23 people, 17 of them by police bullets, according to forensics reports.
Some witnesses to Tuesday's attack spoke of a second bomber, a man aged around 35, who was severely wounded.
"I went into the (station) yard, but a police officer forced me out and said there was a second bomber who did not explode his bomb. I saw him lying on the ground with no legs," said Meral Yildiz, a 50-year-old housewife.
Police did not however confirm the presence of a second bomber at the scene.
There was no immediate claim of responsibility, and Capkin declined to comment on the attacker's possible allegiance.
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Turkey's security forces and police stations are often the target of attacks, many of them by the outlawed Kurdistan Workers' Party (PKK) which took up arms in the southeast in 1984 seeking a separate homeland.
Last month, a car bomb exploded near a police station in the southeastern city of Gaziantep, setting set fire to several vehicles, including a city bus carrying civilians.
Nine people, four of them children, were killed and almost 70 were wounded in the attack blamed on PKK but which was denied by the rebel group.
Gaziantep lies not far from the border with Syria, where a brutal conflict that began as a peaceful uprising against President Bashar al-Assad has now killed around 27,000 people, according to activists.
Turkey, a one-time Syria ally which is now vehemently opposed to Assad's Alawite-led regime, has taken in tens of thousands of refugees from the conflict.
In May, the PKK claimed an attack by two suicide bombers which killed a policeman in the central city of Kayseri.
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.
In November 2010 in Istanbul, a bomber blew himself up on the central Taksim square, wounding 32 people.
The so-called Gazi riots in 1995 were triggered after unidentified assailants randomly opened fire on people in the neighbourhood, killing two people including an Alawite religious leader and wounding dozens more.
Locals blamed the deaths on an inadequate police response and overran police stations, leading to four days of deadly unrest.
The Alawite community, an offshoot of Shiite Islam, numbers around seven million in Sunni-majority Turkey, which has a total population of 73 million.