A suicide bomb attack in front of a police station in central Istanbul injured 32 people on Sunday, 17 of them passers-by, the city's police chief said, dpa reported.
The attacker had tried to force his way on to a police bus in Taksim Square, but was pushed aside before he could detonate his explosives, Huseyin Capkin said.
It was still unclear who was behind the attack, though Turkish media reported it might have been carried out by the outlawed Kurdish Workers Party (PKK), whose self-declared cease-fire expired Sunday.
Two of the policemen injured in the blast were in a serious condition, though nobody had suffered life-threatening injuries, according to officials.
The police maintain a virtual around-the-clock presence at the square, which is popular with tourists and is also used for political demonstrations.
Prime Minister Recep Tayyip Erdogan condemned the attack and laid the blame on separatists.
"Our unity and solidarity are the best answer to those who want to prevent progress in Turkey," he said.
Police on Taksim Square were also the targets of suicide bombings in 1999 and 2001.
Over the past months the PKK has repeatedly called on the Turkish government to declare a cease-fire and open negotiations with its jailed leader Abdullah Ocalan.
Ankara has promised the Kurds more rights but has ruled out talks with the PKK, which is listed by Turkey, the United States and the European Union as a terrorist organization.