ISTANBUL, TURKEY -  JUNE 7: Police officers secure the area near to the scene of a bomb attack which targeted a police bus in the Vezneciler district on June 7, 2016 in Istanbul, Turkey. At least 7 police officers and 4 civilians were killed with a further 36 people wounded after an explosion, believed to have been caused by a bomb, targeted a police bus in central Istanbul according to Istanbul governor Vasip Sahin. (Photo by Defne Karadeniz/Getty Images)