Four people were killed in a suspected Israeli drone attack in Beirut, Lebanon on Tuesday, including a top official with the Palestinian militant group Hamas. Lebanon's Prime Minister Najib Mikati called the attack a "crime" and Hezbollah leader Sayyed Hassan Nasrallah has vowed to retaliate against any Israeli targeting of Palestinian officials in Lebanon. International condemnation has called for an independent investigation into the cause of the explosion, as tensions between Israel and Lebanon continue to rise.