Istanbul,Turkey (CNN) -- A small bomb attached to a bicycle exploded near an overpass in Istanbul's busy Etiler district Thursday morning, injuring at least seven people, police said.
The blast occurred around 9 a.m., during the city's busy morning commute. It damaged five vehicles, police said.
"The explosion happened as we were driving under the overpass with two buses in front of me," taxi driver Yalcin Demirkiran told CNN Turk. "My taxi is left on the scene."
The cause of the blast was not immediately known, according to police who sealed off the area to investigate.
"We heard a big explosion... I saw a big cloud of dust from the window," Banu Yalnizoglu, who lives near where the explosion took place, also told CNN Turk. "People were running and ambulances came."