Istanbul (CNN) -- A suicide bombing at a police station in Istanbul killed at least one police officer and left at least four wounded, police in Turkey said Tuesday. The attacker first threw a hand grenade and then detonated his suicide bomb, Istanbul police chief Huseyin Capkin said in a news conference. Capkin said police had "more or less" determined the identity of the attacker, a male aged about 25 years old, but were not releasing it. The police chief did not link the attacker to any organization. He said there was some uncertainty about the number of wounded. Earlier reports put the number at eight. The blast appears to have taken place at the entrance to the police station in the Sultangazi neighborhood. Ambulances rushed to the scene, according to Turkey's semi-official Anatolia news agency. CNN's Yesim Comert and CNN Turk's Hande Kolcak Kostendil contributed to this report.
NEW: The blast was caused by a suicide bomber, police say . NEW: The attacker throws a hand grenade before exploding his suicide bomb . Ambulances rush to the scene, the Anatolia news agency reports .