Lebanon : Hezbollah leader Hassan Nasrallah is scheduled to hold a large rally . The Lebanese government says a car bomb caused the blast . An unknown group claims responsibility in a YouTube video . The city is a Shia stronghold .
NEW : Hezbollah leader Hassan Nasrallah is scheduled to address a large rally . The Lebanese army says a car bomb caused the blast . An unknown group claims responsibility in a YouTube video . The area is a Hezbollah stronghold .