There was no immediate claim of responsibility. The bomb went off at an Internet cafe frequented by police officers from the headquarters of Istanbul's riot police.
Radical Islamic, Kurdish, and left-wing militants all have a record of carrying out attacks in Istanbul, the largest city in the country.
Turkish militants linked to Al-Qaeda carried out a series of suicide bombings in Istanbul that killed some 60 people in November 2003.
(AP, Reuters, dpa)
