Beirut , Lebanon ( CNN ) -- Lebanese authorities Friday raised the death toll from a car bombing the day earlier , saying at least 22 people were killed and hundreds injured in a southern suburb of Beirut . Thursday 's bomb rocked an area known as a stronghold of the Lebanese Shiite militant group Hezbollah , the Lebanese army said . At least 228 others were injured in the terrorist attack , the Lebanese Internal Security Forces said . There was a heightened security presence Friday in Beirut and other areas of Lebanon , but tensions appeared lower than on Thursday evening . Hezbollah leader Hassan Nasrallah is due to address a large rally Friday in the southern Lebanon town of Aita al Shaab , close to the border with Israel . It 's unclear if Nasrallah will respond to the bombing , which appeared to target Hezbollah , and whether , if so , his words will provoke more anger against the movement and its involvement in Syria 's civil war . The previously planned rally is being held to mark the seventh anniversary of Hezbollah 's July 2006 war with Israel . Along with Shiite-dominated Iran , Hezbollah is helping Syria 's government fight rebels , whose ranks are dominated by Sunnis . After Thursday 's blast , a YouTube video surfaced in which three masked men holding weapons claimed they are part of a group responsible for the attack . They stood before a large Arabic sign containing the Islamic creed , `` There is no God but Allah , and Mohammed is the messenger of Allah . '' The group , which calls itself the Brigade of Aisha , Mother of Believers , accused Hezbollah of being aggressors . Aisha , the last wife of the Prophet Mohammed , is especially revered by Sunni Muslims . In its YouTube post , the group called Nasrallah a `` pig '' and said he works on behalf of Iran and Israel . `` A message : To our brothers and sisters in Lebanon : Stay away from anything to do with Iran -- whether in Beirut or outside Beirut , '' it said . CNN could not confirm the authenticity of the video or the men 's claims . The U.S. Embassy in Beirut tweeted condemnations of the attack . Hezbollah 's involvement in the Syrian conflict has angered some in Lebanon , and many Lebanese fear that the group could be the target of more attacks in future . People living near the scene of Thursday 's blast told CNN they worried that if a car bomb could be brought into this neighborhood , which Hezbollah tightly controls , then others might follow . Many Lebanese see the attack as another indication that Syria 's civil war is spilling over its borders . Lebanon is divided along the same sectarian lines as its neighbor . Lebanon 's army said its units responded immediately to the bombing Thursday evening , setting up a security zone and beginning investigations . Civil defense units were trying to rescue some citizens stuck inside their homes due to the fire resulting from the blast , Lebanon 's National News Agency reported . The explosion came about a month after a car bomb injured dozens of people in the pro-Hezbollah neighborhood of Bir El Abed in a southern Beirut suburb . CNN 's Mohammed Jamjoom reported from Beirut , Lebanon . CNN 's Yasmin Amer reported from Atlanta .
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 .