The Doğan news agency said the bomb went off yesterday in the mainly commercial Maslak district, on the European side of the city.
There was no information on any responsibility claim, but militant leftist, Kurdish and Islamic groups are active in the city. Police were not immediately available for comment. Percussion bombs typically make a loud noise but rarely cause serious damage. The attack comes a day after a police crackdown on radical groups in Istanbul led to a five-hour shootout with a suspected leftist militant that killed three people and injured eight others.
Police are on alert for possible clashes with possible leftist figuress on Labor Day on Friday. Bomb attacks are not uncommon in Turkey, where leftist groups, ethnic separatists and Islamic militants are active.