A bus carrying young Israeli tourists in a Bulgarian resort exploded today, killing at least four people and wounding about 20, police say. Witnesses told Israeli media that the huge blast occurred soon after someone boarded the vehicle. Images showed smoke billowing from the scene in the Black Sea city of Burgas, some 250 miles east of the capital, Sofia. Bulgaria is a popular tourist destination for Israelis, and Israeli tourists have been targeted before, namely in India, Thailand, and Azerbaijan. Iran is suspected of being behind these attacks.